feat: WASM extension versioning with WIT compat checks (#592)

* feat: add WASM extension versioning with WIT compat checks and CI enforcement

Phase 1 — WIT Versioning & Compatibility Checks:
- Version WIT packages as `package near:[email protected];`
- Add `semver` crate for version parsing and comparison
- Add `WIT_TOOL_VERSION` / `WIT_CHANNEL_VERSION` host constants
- Add `version` and `wit_version` fields to capabilities schemas
- Add `wit_version` column to `wasm_tools` DB table (both backends)
- Add load-time `check_wit_version_compat()` with semver rules
- Add `IncompatibleWitVersion` error variants for tools and channels
- Enhance instantiation errors with WIT version mismatch hints
- Update all 14 capabilities JSON and 14 registry JSON files

Phase 2 — Upgrade-in-Place & Channel DB Storage:
- Change tool store to DELETE-before-INSERT (one version per extension)
- Create `wasm_channels` table (PostgreSQL migration + libSQL schema)
- Add `WasmChannelStore` trait with PostgreSQL and libSQL backends
- Add `extension_info` tool showing version, WIT version, and status
- Wire `ExtensionInfoTool` into tool registry (7 extension tools)

Phase 3 — CI Version-Bump Enforcement:
- Add `scripts/check-version-bumps.sh` checking WIT/tool/channel versions
- Add `version-check` CI job (PR-only) to `.github/workflows/test.yml`
- Support `[skip-version-check]` label/commit message bypass

Includes 7 regression tests for WIT version compatibility checking
and 2 integration tests for WIT version annotation verification.

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: address PR review feedback for WASM extension versioning

- Wrap PostgreSQL DELETE+INSERT in transactions for both tool and channel
  store() methods to prevent data loss on partial failure (Gemini, Copilot)
- Rename StoredWasmChannelWithBinary.tool → .channel (copy-paste fix)
- Remove unused WasmError::IncompatibleWitVersion variant (dead code)
- Map channel loader WIT mismatch to IncompatibleWitVersion instead of
  generic Config error, simplify variant to single String message
- Fix extension_info description to match actual returned fields
- Add schema test for ExtensionInfoTool matching existing test pattern
- Fix CI script to fail fast on git errors instead of silent bypass

[skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

wit/tool.wit

@@ -9,7 +9,7 @@
 // - Secrets are NEVER exposed to WASM; credentials are injected at host boundary
 // - All outputs are scanned for secret leakage before returning to WASM
 
-package near:agent;
+package near:agent@0.2.0;
 
 /// Host-provided capabilities for sandboxed tools.
 ///