fix: complete bracketed artifact binding guards

[LloydVickeryASI]

Relationship to the upstream fix

Incremental follow-up to UsefulSoftwareCo/executor#1884, targeting its fix/artifact-hyphenated-tool-paths branch. This branch starts at 3069b15579ff054cfc4fd222a3d44d071392310c; the diff contains only the additions below, not a second copy of the broader hyphenated-path fix.

Changes

• Recognize static single-quoted integration roots as well as double-quoted and dotted roots, including named roles and whitespace.
• Reuse that root grammar in the existing hardcoded-connection guard. Reject immediate user/org segments in dot or bracket notation on both create and edit, with valid bracket syntax in the error guidance.
• Add regression coverage for reserved roots, comments, unrelated tools properties, dynamic expressions, matching/missing/mismatched connections, atomic edit rejection, and create-to-execute-action resolution.
• Document both bracket quote styles in the artifact guide and add a patch changeset.

The connection resolver, ownership checks, available-connection inventory and single-call execution contract are unchanged. Dynamic bracket expressions are not newly supported. Client/host wire serialization remains the parent PR's implementation.

Verification

• Regression-first run against the unchanged parent implementation: 15 failed / 51 passed in the expanded binding suite. After the patch: 66 passed.
• bun run format and bun run format:check: passed.
• bun run lint: passed.
• bun run typecheck: passed across all 45 workspace packages.
• MCP package bun run test: 249 passed across 8 files. The initial sandboxed run could not bind the stdio daemon's loopback listener; the full package passed with local networking available.
• Execution package bun run test src/skills.test.ts: 6 passed.
• bun run test:selfhost scenarios/artifacts.test.ts -t 'create-artifact hands a non-Apps client': 1 passed, 3 unselected. A fresh local instance verified missing single-quoted bindings, create/edit rejection of bracketed pinned paths, unchanged saved source after rejection, and normal artifact rendering.
• Full monorepo bun run test and the full cross-target E2E matrix were not run. This is a draft, not a merge/deployment request.

Recorded end-to-end evidence

The recording shows the valid artifact still rendering after the negative MCP checks. The rejection/no-persistence assertions are in the scenario source; they are not represented as browser error banners in this recording. All data is synthetic test content.