fix(server): bound watcher work for late ignored directories

Refresh Git exclusions when ignored directories appear after subscription and bound Linux and native classification work. Preserve tracked-file notifications, ignore-update barriers, and watcher recovery.

Fixes #4558. Supersedes #4808 by @Marcus172; this change incorporates six commits originally authored by Marek Rom and adds verified follow-up fixes. The independent session-context leak is fixed by #5208. Combined isolated daemon verification passed.

Co-authored-by: Marek Rom <marek.marcus.rom@gmail.com>

docs/file-observation.md

@@ -10,12 +10,12 @@ Closing an observation must remain safe after its root is renamed or removed. Wo
 
 Linux topology repair is trailing-debounced and scoped to the renamed path. A file rename needs one classification stat; a new or moved directory scans only its subtree. Full-tree scans are reserved for startup and ignore-set replacement. The initial Linux scan conservatively emits existing files discovered before their directory watcher was installed; WorkspaceGit batches these into one refresh. Benchmark this startup cost with pre-populated trees.
 
-Windows and macOS use one native recursive watcher plus an ignored-pruned, directory-indexed inventory. Native events deliver immediately. Named events trigger serialized shallow scans of their parent directories; known directory events also reconcile that subtree. This recovers concrete create and delete paths omitted by coalescing without walking the whole root for each edit. Startup and exclusion changes use an awaited full inventory barrier. Activity arms a full safety audit 30 seconds after it settles, with a 30-second minimum interval and a five-minute starvation bound; pathless native events also trigger an immediate shallow root scan. Observation fails into polling rather than retaining more than 250,000 file and directory entries per root.
+Windows and macOS use one native recursive watcher plus an ignored-pruned, directory-indexed inventory. Native events deliver immediately. Named events trigger serialized shallow scans of their parent directories; known directory events also reconcile that subtree. This recovers concrete create and delete paths omitted by coalescing without walking the whole root for each edit. Classification is admission-controlled to 32 concurrent `fs.stat` calls, since `fs.stat` runs on the libuv threadpool the whole daemon shares. Startup and exclusion changes use an awaited full inventory barrier. Activity arms a full safety audit 30 seconds after it settles, with a 30-second minimum interval and a five-minute starvation bound; pathless native events also trigger an immediate shallow root scan. Observation fails into polling rather than retaining more than 250,000 file and directory entries per root.
 
-Read aggregate health from the owning observer service. Runtime metrics include active observations, native handles, tracked native files, pending events and immediate reconciliation work, scoped and full reconciliation activity and latency, and failure counts. Delayed safety audits do not count as pending work. Closing the service releases every subscription and clears its diagnostics. Do not add path lists, watcher handles, or platform-specific controls to this interface.
+Read aggregate health from the owning observer service. Runtime metrics include active observations, native handles, tracked native files, pending events and immediate reconciliation work, scoped and full reconciliation activity and latency, and failure counts. `nativeTrackedFileCount` and other per-file counters are native-backend diagnostics only — the Linux backend keeps no per-file inventory and reports zero — so a cross-platform assertion belongs on delivered events, not those counters. Delayed safety audits do not count as pending work. Closing the service releases every subscription and clears its diagnostics. Do not add path lists, watcher handles, or platform-specific controls to this interface.
 
 Git owns Git-ignore evaluation. The observer accepts absolute excluded roots and applies updates without replacing the observation or exposing its watcher topology. This keeps tracked files inside otherwise ignored directories observable and keeps Git policy out of the filesystem module.
 
-Workspace Git verifies each repository metadata subscription with a one-shot canary inside the Git directory. If the event does not round-trip through the subscription callback, treat the watcher as unavailable and enter degraded polling. Refresh working-tree Git-ignore exclusions from ignore-file events and watcher recovery, never from a healthy-watcher timer.
+Workspace Git verifies each repository metadata subscription with a one-shot canary inside the Git directory. If the event does not round-trip through the subscription callback, treat the watcher as unavailable and enter degraded polling. Refresh working-tree Git-ignore exclusions from ignore-file events, newly observed directories, and watcher recovery, never from a healthy-watcher timer. `git ls-files` reports an ignored directory only once it exists, so new directory topology is a trigger in its own right; the refresh is edge-triggered per directory and debounced so a dependency install collapses into a couple of Git runs.
 
 The real-filesystem contracts and daemon auto-archive lifecycle run in the normal server test suite. Use the scripts only for manual performance and soak work: `npm run measure:file-observer --workspace=@getpaseo/server` measures burst and sustained-create behavior, and `npm run repro:file-observer-teardown --workspace=@getpaseo/server` runs the teardown soak.