fix(mcp): make loopover-mcp CLI failures respect --json

[RealDiligent]

Summary

• Add packages/loopover-mcp/lib/cli-error.js mirroring @loopover/miner's { ok: false, error } contract
• Wrap top-level runCli dispatch in try/catch so thrown errors never escape as raw Node stack traces
• Extend mcp-cli harness with runExpectingFailure and tests for unknown command, missing --login, and unsupported --agent-profile failures with --json

Closes #5928

Test plan

• npx vitest run test/unit/mcp-cli-basics.test.ts (21/21 pass)
• npx vitest run test/unit/mcp-cli- (125/128 pass; 3 symlink rejection tests fail on Windows only — pre-existing)

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.24%. Comparing base (0760e1f) to head (478b126).
⚠️ Report is 23 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6104   +/-   ##
=======================================
  Coverage   95.24%   95.24%           
=======================================
  Files         595      595           
  Lines       47035    47046   +11     
  Branches    15015    15015           
=======================================
+ Hits        44797    44808   +11     
  Misses       1493     1493           
  Partials      745      745           

Flag	Coverage Δ
shard-1	44.01% <ø> (+<0.01%)	⬆️
shard-2	36.68% <ø> (+0.06%)	⬆️
shard-3	32.08% <ø> (+0.02%)	⬆️
shard-4	33.60% <ø> (+0.47%)	⬆️
shard-5	31.66% <ø> (-0.57%)	⬇️
shard-6	44.50% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[loopover-orb]

Caution

🟥🟥🟥🟥🟥🟥🟥🟥🟥🟥🟥🟥

🛑 LoopOver review result - fixes required

_{Review updated: 2026-07-15 09:48:53 UTC}

5 files · 1 AI reviewer · no blockers · readiness 80/100 · CI failing · blocked

🛑 Suggested Action - Fix Blockers

Review summary
This PR wraps the top-level CLI dispatch in bin/loopover-mcp.js in a try/catch so thrown errors are converted to the miner's established `{ ok: false, error }` JSON contract (via the new lib/cli-error.js) instead of leaking raw Node stack traces, mirroring the pattern already used in @​loopover/miner per test/unit/miner-cli.test.ts. The harness changes (runExpectingFailure, folding stdout into thrown Error messages) are correctly scoped support code for the new tests, and the new mcp-cli-basics.test.ts assertions exercise both the --json and plain-text failure paths for three distinct failure sources (unknown command, missing --login, unsupported agent profile). The change closes #5928 and is narrowly targeted at the stated bug.

Nits — 5 non-blocking

• cli-error.js:22 `argsWantJson` only recognizes `--json`/`--json=...`; worth confirming this matches whatever flag-parsing convention the rest of loopover-mcp.js uses elsewhere so `--json` combined with other flag syntaxes isn't missed.
• bin/loopover-mcp.js:591 if a command partially writes to stdout before throwing, the JSON failure object from `reportCliFailure` would be appended after that partial output, breaking the 'parseable JSON on stdout' guarantee for --json — worth confirming none of the wrapped commands stream partial output before failing.
• test/unit/support/mcp-cli-harness.ts:29 the comment explaining why stdout is folded into the Error message is helpful, but the same fold-in logic is now duplicated across `run` and `runAsync`/`runExpectingFailure`; consider a shared helper to avoid drift.
• Add a short code comment or test asserting that non-JSON-mode failures never touch stdout (already partially covered by the `plainFailure.stdout` assertion) to lock in the contract long-term.
• Consider exporting a shared `foldStreamsIntoError` helper in mcp-cli-harness.ts used by both `run` and `runAsync` to reduce duplication.

CI checks failing

• validate
• validate-code

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ Linked	#5928
Related work	⚠️ 2 scoped overlaps	Top overlaps are listed below; lower-confidence bulk is hidden.
Change scope	❌ 8/20	High review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 352 registered-repo PR(s), 170 merged, 29 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	RealDiligent; Gittensor profile; 352 PR(s), 29 issue(s).
Gate result	✅ Passing	No configured blocker found.
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Addressed
The PR adds a cli-error.js module mirroring the miner's reportCliFailure/argsWantJson/describeCliError contract, wraps the top-level runCli dispatch in try/catch to route failures through it, and adds harness support plus tests covering unknown command, missing --login, and unsupported --agent-profile failures under --json (and confirms non-json stderr behavior is preserved).

Review context

• Author: RealDiligent
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 352 PR(s), 29 issue(s).
• Related work: Items reference the same linked issue fix(mcp): loopover-mcp CLI errors never respect --json, unlike @loopover/miner's cli-error contract #5928. (issue #5928)
• Related work: Open PR work references issue fix(mcp): loopover-mcp CLI errors never respect --json, unlike @loopover/miner's cli-error contract #5928. (issue #5928)

Contributor next steps

• Start here: Review top overlaps.
• Then work through the remaining 2 steps in the Signals table above.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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[loopover-orb]

LoopOver is closing this pull request on the maintainer's behalf (CI is failing (validate, validate-code)). This is an automated maintenance action — to pursue this change, please open a new pull request with the issues resolved. Closed PRs may be analyzed later to improve review accuracy, but they are not automatically reopened or re-reviewed.