fix(lcm)!: store LCM sessions under their store scope

[ScriptedAlchemy]

Summary

• Session rows that LCM creates before the rollout projection now take the project fields of the session store they live in (project_id/project_id for a project session store, user/user for the profile session store) instead of an invented unknown project. The rollout projection's working directory then only refines project_path.
• The placeholder-replacement special case in observation reconcile is deleted, with LCM_UNKNOWN_PROJECT_KEY, LCM_LEGACY_PLACEHOLDER_PROJECT_KEY, and lcm_unscoped_session_project. A scope-shaped row merges through the ordinary reconcile rules.
• LCM schema 13 → 14. Coordinator decision: the shipped-v13 admission guarantee (shipped_v13_profile_remains_admissible_for_projector_rebuild, cf4b1a2) is a compatibility promise the project no longer makes. A shipped v13 session store can hold LCM rows with the invented project; it is refused typed, listed in reset_required_stores, and recreated empty by the scoped tracedecay wipe --stale --yes (same shape as the session-temporal v6→v7 bump in perf(sessions)!: extend session generations, don't copy them #2761). No migration, no legacy-row repair.

Changes

• tracedecay-store: session_project_fields(scope) is the one scope → (project_key, project_path) authority; StoreShardScopeV1::session_scope() names the scope of a shard's sessions (None for non-session shards).
• tracedecay-lcm: compress, compress_retained_page, record_session_boundary take the store's ObservationScopeV1; ensure_session is private and leaves started_at unset; new LcmError::NotASessionStore (not_a_session_store, non-retryable); LCM_SCHEMA_VERSION = 14.
• tracedecay-sessions / tracedecay-global-db: SessionStoreAccess::lcm_session_scope() resolves the scope from the registered binding and refuses non-session stores before a write transaction; reconcile's placeholder early return is removed.
• The earlier "keep v13 and repair its shell rows" commit (fab4913) is reverted.
• Tests: schema::tests::shipped_v13_profile_remains_admissible_for_projector_rebuild is replaced by shipped_v13_profile_refuses_typed_without_upgrading (v13 marker → ProfileResetRequired { found_version: Some(13), required_version: 14 } from admission and from ensure_lcm_schema, marker left at 13). The transport acceptance case is now session_stores_at_shipped_lcm_schema_13_refuse_sessions_only_until_their_scoped_reset: a real daemon over a profile whose project and profile session stores are aged to 13 keeps serving code, refuses session reads typed with the wipe --stale --yes remedy, doctor counts both as pending operator actions, the scoped reset deletes exactly those two stores (every other profile file byte-identical), and the restarted daemon serves sessions with an empty census.

Fail before / pass after

• cargo test -p tracedecay-lcm --lib -- schema::tests::shipped_v13 with LCM_SCHEMA_VERSION set back to master's 13: FAILED a shipped v13 store must refuse admission: Current. With 14: ok.
• session_project_rebind_tests::lcm_compression_before_the_rollout_stores_the_session_under_its_store_scope fails on master (row stored as ("unknown", "unknown")), passes here; a_rollout_starting_after_lcm_compression_keeps_its_own_start_time fails without the started_at fix.

Runtime proof (debug tracedecay built from this branch, isolated HOME/TRACEDECAY_DATA_DIR, daemon under systemd-run --user --scope -p MemoryMax=6G)

fresh markers: project=14 profile=14
== age both session stores to the shipped LCM schema 13
reset_required_stores: [{"authority":"LCM","found_version":13,"reason":"LCM profile schema 13 is incompatible with required schema 14; reset the profile","remedy":"tracedecay wipe --stale --yes","required_version":14,"store":"profile sessions"},{"authority":"LCM","found_version":13,"reason":"LCM profile schema 13 is incompatible with required schema 14; reset the profile","remedy":"tracedecay wipe --stale --yes","required_version":14,"store":"project sessions proj_860e8e21b6515288"}]
lcm_status project: {"kind":"reset_required","authority":"LCM","found":13,"required":14,"remedy":"tracedecay wipe --stale --yes"}
lcm_status user:    {"kind":"reset_required","authority":"LCM","found":13,"required":14,"remedy":"tracedecay wipe --stale --yes"}
== tracedecay wipe --stale --yes
wipe exit 0
reset profile sessions (4 entries removed from …/.tracedecay); the daemon recreates it empty
reset project sessions proj_860e8e21b6515288 (5 entries removed from …/.tracedecay/projects/proj_860e8e21b6515288); the daemon recreates it empty
reset_required_stores after reset: []
lcm_status project: null   (no problem)
rebuilt markers: project=14 profile=14

Verification (local; CI not consulted)

• cargo test -p tracedecay-store -p tracedecay-lcm -p tracedecay-sessions -p tracedecay-session-runtime -p tracedecay-global-db (test-helpers): global_db lib 389, registered_schema_fail_closed 1, session_relation_graph 8; lcm lib 166 (2 ignored, as on master), lcm_suite 15; session_runtime lib 129, session_store_read_cost 7; sessions lib 539; store lib 73, store_suite 52; hotpath_coverage 1 each.
• cargo test -p tracedecay --features test-transport,test-helpers: session_suite 437 passed; full mcp_suite 617 passed; transport_acceptance_suite -- stale_sessions_store_reset 6 passed (re-run on the final merged tip).
• cargo clippy -p tracedecay-store -p tracedecay-lcm -p tracedecay-sessions -p tracedecay-session-runtime -p tracedecay-global-db -p tracedecay --all-targets (test features) -D warnings: clean. cargo fmt --all -- --check: clean.
• cargo check --workspace --all-targets --target x86_64-pc-windows-gnu --features tracedecay/test-transport,tracedecay/test-helpers,tracedecay-cli/test-transport: exit 0.
• Wire contract unchanged (NotASessionStore maps to existing failed/unavailable states); @tracedecay/sdk unchanged, the refusal surfaces as the existing reset_required problem.

BREAKING CHANGE: LCM schema 14. Session stores at LCM schema 13 (every profile written since v1.0.0-beta.50) refuse session features as reset-required for the LCM component (found 13, required 14) until tracedecay wipe --stale --yes resets exactly those session stores; code intelligence keeps serving meanwhile. LCM-created sessions now carry their store's project or profile scope instead of an invented unknown project.

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[ScriptedAlchemy]

Resolved the blocker above with option 1 in fab4913 (after merging current master in f5e8b93): LCM stays at schema 13, so shipped v13 profiles stay admissible (master's shipped_v13_profile_remains_admissible_for_projector_rebuild passes), and observation reconcile again replaces the legacy unknown / lcm-active-context shell rows those stores hold (now a private check in observation_projection/state.rs). New LCM rows still carry session_project_fields(scope). The change is no longer breaking, so I dropped the ! from the title; the BREAKING CHANGE footer in the description is stale and should not go into the squash commit.

[devin-ai-integration]

Devin Review found 1 new potential issue.

🐛 1 issue in files not directly in the diff

🐛 Legacy LCM sessions remain under invented projects

Admitting version-13 stores leaves LCM-only sessions under unknown or lcm-active-context. ensure_session never updates existing rows, and reconciliation runs only when an observation arrives. Project-scoped session reads cannot find those sessions.