Manifest capability omission silently breaks whole-extension activation (CI green, package ships broken) #103

Summary

When an extension's manifest.json capabilities array omits a capability that the extension code actually uses (e.g. the code calls api.registerPreflight(...) but "preflight" is not declared), the SDK gates the register* call and the entire extension silently fails to activate — none of its commands, importers, hooks, etc. work. Crucially, npm test/CI stay green and npm publish succeeds, so a completely non-functional package can ship undetected.

Real-world impact

pm-github@2026.6.2 shipped with a manifest missing "preflight" while index.ts calls registerPreflight. Result: the published package failed activation entirely (extension_activate_failed) — import/export/sync/all commands were dead — yet CI was green and the version published normally. The failure is only visible via pm extension --doctor --detail deep.

Repro

1. An extension whose activate() calls e.g. api.registerPreflight(...) (or registerSearchProvider, registerItemFields, …).
2. Omit the corresponding token from manifest.json capabilities.
3. pm install <ext> → install/build/test all succeed.
4. Run any of the extension's commands → "Unknown command" / silent no-op. pm extension --doctor --detail deep shows activation_status_totals: failed:1.

Suggested fixes (any of)

• Load-time error: when a register* call is gated out by a missing capability, surface a clear error/warning naming the offending call and the capability to add — instead of silently dropping activation.
• release:check/pack-time lint: cross-check register* calls against declared capabilities and fail the build on mismatch. This would have caught the regression before publish.
• At minimum, make the doctor failure non-silent on a normal command invocation.

Found while functionally testing the pm extension ecosystem against pm-cli 2026.5.31.