fix(mcp): make cleanup failures observable

[sethkarten]

Core-06: observable MCP cleanup failures

Draft publication for stack visibility.

Scope

• observable/redacted MCP session close failures
• focused cleanup regression coverage
• two-path incremental delta only

Validation

• focused MCP probe + Core-05 declaration tests: 17/17
• Biome changed paths: green
• git diff --check: green
• root tsgo is blocked by the parent Core-05 test-helper composition error (sdk-mcp-boundary.test.ts missing invokeHostRequest); remediation is proceeding append-only on feat(core): enforce project MCP trust boundaries #1263.

Parent: Core-05 #1263 at 6e8e33c484a26498d41022accd5f118ebe7822fc
Head: 1fc9d92c3682f98fe672d9cf812ac44a6dcded3a

Note

Make MCP cleanup failures observable

Adjusts blank line formatting in the MCP cleanup code with no functional changes.

^{Macroscope summarized 940ce7f.}

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Note

Low Risk
Intended scope is observability and tests around MCP teardown, not auth or declaration admission; risk rises only if close-path behavior changes beyond logging/reporting.

Overview
Core-06 incremental delta on the MCP declaration/runtime stack (parent Core-05): make MCP session close / cleanup failures observable instead of failing silently, using redacted error detail so operators can see that teardown failed without leaking secrets.

The PR description also calls for focused regression coverage around MCP probe / declaration cleanup paths. The diff snapshot provided for this review contained no file changes, so line-level verification should be done on the branch head (1fc9d92); an earlier automated pass on a nearby commit reported whitespace-only edits in MCP cleanup code.

^{Reviewed by Cursor Bugbot for commit 940ce7f. Bugbot is set up for automated code reviews on this repo. Configure here.}

[sethkarten]

Superseded as part of the physical Core/MCP stack split. This PR’s final tree is identical to #1263 and contributes no unique delta; MCP work continues in #1337 and #1338. Closing this PR to avoid duplicate review; branch retained for provenance.