chore(tools): add FTB Chunks -> Xaero's map reveal migration tooling

The swap does not carry players' explored terrain across. FTB Chunks stores no
rendered map (its region zips hold chunks.dat plus five data PNGs, one of which
packs height into an image channel), and Xaero's region format is closed and now
version 6 with per-pixel NBT blobs, so the community converters no longer work.
Rather than convert pixels, prune a copy of the world save down to exactly the
chunks a player revealed and let Xaero's own generator map it.

Validated against real data: extracting the 167-region / 98,170-chunk mask
cross-checks clean against FTB's own pixel data, and Anvil pruning round-trips
byte-identically (15.7 MB -> 471 KB on a live region file, slot-to-chunk mapping
confirmed against 1024 chunk NBT headers).

Deferred for now: needs the world save and one singleplayer pass per player.
See analysis/FTB-XAERO-MAP-MIGRATION.md.

analysis/FTB-CHUNKS-SWAP.md

@@ -0,0 +1,139 @@
+# FTB Chunks -> Open Parties and Claims + Xaero's maps
+
+**Status:** implemented in the pack (working tree, uncommitted) - 2026-09-30
+**Decision:** replace FTB Chunks with **Open Parties and Claims (OPAC)** for claims/forceloading and
+**Xaero's World Map + Minimap** for mapping. FTB Teams, FTB Quests, FTB Library, FTB XMod Compat and
+FTB Backups 3 all stay.
+**Accepted cost:** every player re-claims their land and re-creates their waypoints.
+
+Confidence tags follow `FINDINGS.md`: **VERIFIED** / **DOCUMENTED** / **COMMUNITY** / **INFERENCE**.
+
+---
+
+## 1. Why this works at all
+
+The pack's earlier review (`MODLIST-REVIEW.md` §8) recommended keeping FTB Chunks on the grounds that
+"wholesale replacement breaks FTB Quests/Teams". That is only true of a *wholesale* FTB removal.
+**VERIFIED:** FTB Quests' build declares `ftb-library` + `ftb-teams` as required and `ftb-xmod-compat`
+as optional - **not** FTB Chunks. FTB Quests also ships **no** claim-chunk task type. So FTB Chunks is
+the one mod in the FTB suite that can leave without touching quests, provided Teams stays.
+
+**VERIFIED:** nothing else in the pack declares FTB Chunks as a required dependency. The only
+cross-mod hooks are inside FTB XMod Compat (KubeJS/GameStages progression, rank-based claim limits),
+which degrade to inert modules.
+
+## 2. What changed
+
+| Action | Path |
+| --- | --- |
+| Removed | `mods/ftb-chunks-forge.pw.toml` (was `ftb-chunks-neoforge-2101.1.22`, CF 314906) |
+| Removed | `config/ftbchunks-client.snbt` (the `minimap.enabled=true` modpack default) |
+| Edited | `.packwizignore` - dropped `config/*` + `!config/ftbchunks-client.snbt`, back to `config/` |
+| Added | `mods/open-parties-and-claims.pw.toml` - `neoforge-1.21.1-0.31.6` (`side = "both"`) |
+| Added | `mods/xaeros-world-map.pw.toml` - `neoforge-1.21.1-1.46.0` (`side = "both"`) |
+| Added | `mods/xaeros-minimap.pw.toml` - `neoforge-1.21.1-26.5.0` (`side = "both"`) |
+| Added | `mods/xaeros-minimap-world-map-waystones-compatibility-forge.pw.toml` - `2.1.0` |
+| Regenerated | `index.toml` (147 entries) and the `[index]` hash in `pack.toml` |
+
+Net: **146 mods** (138 Modrinth/other + 8 CurseForge), down from 9 CurseForge-exclusive mods. All four
+new mods are Modrinth-hosted, so they are checkable by `packwiz update`.
+
+The three Xaero's entries are byte-identical to the ones deleted in `b0542f9` (2026-09-28) - same
+versions, same sha512s - so this is a revert of the map half of that commit, not a new integration.
+
+## 3. Where the pack traded one thing for another
+
+| FTB Chunks capability | Replacement | Notes |
+| --- | --- | --- |
+| Chunk claims + protection | OPAC | Server config now lives in the world save, not the pack. |
+| Forceload + offline ticking | OPAC `claims.forceload.offlineForceload` | Farms-vs-TPS trade is unchanged; reliability is less proven (see §5). |
+| Minimap + fullscreen map | Xaero's Minimap + World Map | Now two client mods instead of one. |
+| Waypoints + teleport | Xaero's Minimap | **No migration path** - see §4. |
+| Party/team claims | OPAC `primaryPartySystem` = FTB Teams | Must be set, or OPAC runs its own parallel party system. |
+| Waystones on the map | `xaeros_waystones_compatibility` | Restored; it had been removed with the maps. |
+| FTB Ranks permission overrides | `xaero.pac_max_claims` / `xaero.pac_max_forceloads` | Moot in practice: FTB Ranks was never installed. |
+
+## 4. Migration runbook (server operator)
+
+**Before the update**
+1. Take a world backup. FTB Chunks' claim data stays in the save after the mod is removed, so this
+   backup is the rollback path.
+2. Have each player screenshot or export their FTB Chunks waypoints. They live client-side under
+   `local/ftbchunks/`; **there is no FTB Chunks -> Xaero's converter** (only JourneyMap -> Xaero tools
+   exist). Re-entry is manual.
+3. Capture who owned which claims/forceloads, so players have a checklist and an admin can pre-claim
+   using OPAC server-claim mode if desired.
+
+**Cutover (one update, low-activity window)**
+4. Do **not** run FTB Chunks and OPAC side by side - two claim systems means split protection logic.
+   Hard cutover.
+5. Start the server once with OPAC installed so it generates
+   `world/serverconfig/openpartiesandclaims-server.toml`, then **stop the server**.
+6. Edit the generated file (it carries `# Default:` comments for every key) and set at minimum:
+   - `maxPlayerClaims = 500` (matches the old FTB Chunks cap)
+   - `maxPlayerClaimForceloads = 25` (**decided 2026-09-30**; the stock default is lower, so leaving it
+     alone silently removes forceloading)
+   - `primaryPartySystem` -> FTB Teams
+   - a decision on `claims.forceload.offlineForceload` (farms while offline vs TPS)
+   - add `claims.forceload.offlineForceload` to `playerConfigurablePlayerConfigOptions` /
+     `opConfigurablePlayerConfigOptions` if players should be able to toggle their own
+7. Re-claim: each player re-claims their base and re-forceloads, via the OPAC UI (`'`) or the Xaero's
+   world map (right-click / drag-select).
+
+**After**
+8. Verify per-player forceloading actually keeps chunks ticking with the owner offline. This is the
+   known weak point (§5).
+9. Verify protection across the modded stack - especially Create contraptions, Sable ships, and
+   fake-player automation.
+10. Re-tier any rank/permission limits you were relying on.
+
+## 5. Risks and open items
+
+- **OPAC force-loading reliability is the one thing that can invalidate the swap.** Open upstream
+  issues report chunks marked forceloadable but never actually loaded (#855, #927, plus #237/#528).
+  **COMMUNITY.** Test before trusting; re-test on every OPAC bump. If it fails, this swap should be
+  rolled back - forceloading is the one feature the pack cannot work around.
+- **OPAC is self-described beta** and releases frequently (0.31.6, 2026-09-10). **DOCUMENTED.**
+- **OPAC and Xaero's are version-coupled** - OPAC's README tells users to keep the Xaero's mods on
+  their latest versions. Bump them together.
+- **Claim protection parity is unverified.** OPAC protects vanilla plus a supported-mod list (Create is
+  built in on Forge), and needs manual exception entries for anything else. Open reports exist for
+  creeper explosions (#731) and modded projectiles (#758) inside claims. **COMMUNITY.** The pack's
+  Apotheosis/Sophisticated/Ars Nouveau/Alex's Mobs surface needs a pass.
+- **Sable / Create Aeronautics.** A crash with Sable contraptions was reported (#873) and is **closed**,
+  but was not re-verified against 0.31.6. **COMMUNITY.** Ships are not covered by plain chunk claims
+  under either system; the pack has no ship-claim mod. Options if that matters:
+  `aeroclaims` ("Create Aeronautics: Claims", NeoForge 1.21.1, works with **OPAC or FTB**), or
+  `sable-protect`. Note that dropping FTB Chunks does close the door on `ftbchunksaerospace` and
+  `Create-Aeronautics-FTB-Chunks`.
+- **Licensing.** OPAC is **LGPL-3.0** - no pack conditions. Xaero's World Map and Minimap are
+  **All Rights Reserved**: because this pack is distributed from `git.ljones.me` and not from
+  CurseForge/Modrinth, the terms require an **easily accessible credit link to an official Xaero page**
+  in the pack. Add one. **VERIFIED** (from the mods' own "Modpacks and Other" sections).
+- **`side = "both"` for Xaero's** puts them on the server too. That buys reliable multi-world map
+  identity and server-side map profiles, and matches the pre-`b0542f9` configuration, but the server
+  then registers status effects that stop *vanilla* clients joining unless disabled in
+  `config/xaero/*`. All players get mods via packwiz, so this is not expected to matter.
+- **Vanilla-client / optional-client is actually improved** for claims: OPAC's client side is optional,
+  so a player without it is still protected and can use `/oclaims` chat commands.
+
+## 6. Rollback
+
+Re-add `mods/ftb-chunks-forge.pw.toml` (and the client config if the minimap default is wanted) and
+`packwiz refresh`. FTB Chunks' claim/forceload data is untouched in the world save, so existing claims
+resume. Then remove OPAC and the Xaero's mods. Keep the pre-swap world backup regardless.
+
+## 7. Docs that need follow-up
+
+- **Map/waypoint rescue from the old FTB data** - see `analysis/FTB-XAERO-MAP-MIGRATION.md` and the
+  `tools/ftbchunks-reveal.py` + `tools/prune-world-to-reveal.py` scripts. Mask extraction is validated;
+  the world-save pruning step is written and unit-tested but not yet run.
+
+- `FINDINGS.md` - §3.3, §7.1, §8 rows 2-3, appendix A and appendix B updated in this change; §1's
+  mod-count statistics were left at their earlier snapshot (a note was added).
+- `MODLIST-REVIEW.md` §7.4 and §8 still say Open Parties and Claims is a SKIP/duplication and "Keep
+  FTB". **Stale** - the swap is now the intended design.
+- `MODLIST-GROUPS.md` / `analysis/master-table.md` / `analysis/groups-table.md` carry the same stale
+  OPAC verdict.
+- Not done: re-adding `xaero-train-map` (was `Ov2r3aVY`, 1.0.0). It is unblocked again by this change and
+  the pack has Create trains; one-line addition if wanted.