fix(channelserver): correct session handler retail mismatches (#167)

Lobby search now returns only quest-bound players (QuestReserved) instead
of all reserved slots, matching retail behavior. The new field is
pre-collected under server lock before stage iteration to respect
Server.Mutex → Stage.RWMutex lock ordering.

Replaced three TODOs with RE documentation from Ghidra decompilation of
mhfo-hd.dll ZZ:
- Log key off-by-one: putRecord_log/putTerminal_log pass size 0 for the
  key field in ZZ, so the stored key is unused beyond issuance
- User search padding: ZZ per-entry parser confirms 40-byte block via
  memcpy(dst, src+8, 0x28); G2 DLL analysis inconclusive (stripped)
- Player count: field at entry offset 0x08 maps to struct param_1[0xe]

docs/technical-debt.md

@@ -29,9 +29,9 @@ These TODOs represent features that are visibly broken for players.
 | ~~`model_character.go:88,101,113`~~ | ~~`TODO: fix bookshelf data pointer` for G10-ZZ, F4-F5, and S6 versions~~ | ~~Wrong pointer corrupts character save reads for three game versions.~~ **Fixed.** Corrected offsets to 103928 (G1–Z2), 71928 (F4–F5), 23928 (S6) — validated via inter-version delta analysis and Ghidra decompilation of `snj_db_get_housedata` in the ZZ DLL. | [#164](https://github.com/Mezeporta/Erupe/issues/164) |
 | `handlers_achievement.go:117` | `TODO: Notify on rank increase` — always returns `false` | Achievement rank-up notifications are silently suppressed. Requires understanding what `MhfDisplayedAchievement` (currently an empty handler) sends to track "last displayed" state. | [#165](https://github.com/Mezeporta/Erupe/issues/165) |
 | ~~`handlers_guild_info.go:443`~~ | ~~`TODO: Enable GuildAlliance applications` — hardcoded `true`~~ | ~~Guild alliance applications are always open regardless of setting.~~ **Fixed.** Added `recruiting` column to `guild_alliances`, wired `OperateJoint` actions `0x06`/`0x07`, reads from DB. | [#166](https://github.com/Mezeporta/Erupe/issues/166) |
-| `handlers_session.go:410` | `TODO(Andoryuuta): log key index off-by-one` | Known off-by-one in log key indexing is unresolved | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
-| `handlers_session.go:551` | `TODO: This case might be <=G2` | Uncertain version detection in switch case | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
-| `handlers_session.go:714` | `TODO: Retail returned the number of clients in quests` | Player count reported to clients does not match retail behavior | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
+| ~~`handlers_session.go:410`~~ | ~~`TODO(Andoryuuta): log key index off-by-one`~~ | ~~Known off-by-one in log key indexing is unresolved~~ **Documented.** RE'd from ZZ DLL: `putRecord_log`/`putTerminal_log` don't embed the key (size 0), so the off-by-one only matters in pre-ZZ clients and is benign server-side. | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
+| ~~`handlers_session.go:551`~~ | ~~`TODO: This case might be <=G2`~~ | ~~Uncertain version detection in switch case~~ **Documented.** RE'd ZZ per-entry parser (FUN_115868a0) confirms 40-byte padding. G2 DLL analysis inconclusive (stripped, no shared struct sizes). Kept <=G1 boundary with RE documentation. | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
+| ~~`handlers_session.go:714`~~ | ~~`TODO: Retail returned the number of clients in quests`~~ | ~~Player count reported to clients does not match retail behavior~~ **Fixed.** Added `QuestReserved` field to `StageSnapshot` that counts only clients in "Qs" stages, pre-collected under server lock to respect lock ordering. | [#167](https://github.com/Mezeporta/Erupe/issues/167) |
 | `msg_mhf_add_ud_point.go:28` | `TODO: Parse is a stub` — field meanings unknown | UD point packet fields unnamed, `Build` not implemented | [#168](https://github.com/Mezeporta/Erupe/issues/168) |
 
 ### 2. Test gaps on critical paths