fix(omo-senpi): skip drvfs config watchers

[code-yeongyu]

Fixes #6450

Supersedes stale community PR #7368.

Root cause

On WSL, Windows drives are Plan 9/v9fs mounts (statfs().type === 0x01021997). Senpi expands dir config-watch targets into recursive watches, so project and ancestor targets can block while traversing a drvfs tree. Current dev had no filesystem-type guard.

Changes

• Add a Linux-only statfsSync filesystem-type probe with an injectable seam for deterministic tests.
• Skip project .omo config targets and ancestor creation targets when the project cwd is on Plan 9.
• Skip user-config targets only when the user-config path itself is on Plan 9; native user-config targets remain watched even when the project is on drvfs.
• Preserve startup config loading and all non-Plan-9 behavior.
• Regenerate the committed Senpi omo.js extension bundle.

Test evidence

• TDD RED: focused paths suite failed 1 assertion (14 passed, 1 failed) because the simulated Plan 9 project still emitted an ancestor target.
• GREEN: bun test packages/omo-senpi/src/components/config-watch: 39 passed, 0 failed.
• Typecheck: bunx tsgo --noEmit -p packages/omo-senpi/tsconfig.json passed.
• Bundle freshness: node packages/omo-senpi/plugin/scripts/build-extension.mjs --check passed.
• Live isolated Senpi QA: node packages/omo-senpi/scripts/qa/drive.mjs returned PASS, with realSenpiUntouched: true.
• Evidence: .omo/evidence/omo-senpi-adapter/20260829-drvfs-config-watch/README.md

Residual risk

This macOS runner cannot provide an actual WSL Plan 9 mount, so the drvfs branch is tested via the injected filesystem identity seam and exact magic value. The live adapter driver uses an isolated Senpi agent directory and does not exercise a real drvfs mount.

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Summary by cubic

Fixes #6450 by skipping config-watch targets on WSL's Plan 9 (drvfs) filesystem so recursive watches no longer block while traversing those trees.

Changes

• Adds a Linux-only statfsSync filesystem-type probe with an injectable seam for deterministic tests.
• Skips project .omo targets and ancestor creation targets when the project cwd is on Plan 9.
• Skips user-config targets only when the user-config path itself is on Plan 9; native user-config targets remain watched.
• Preserves startup config loading and all non-Plan-9 behavior, and refreshes the committed omo.js extension bundle.

^{Written for commit 2c926a5. Summary will update on new commits.}