test(cli): kill the surviving mutants of the copilot, codex and opencode profiles

[blafourcade]

🎯 What & why

Last lot of #799: the three tool-profile scopes left below target. Each held a floor under 90, so a profile's build contract or path mapping could change without any test noticing. This PR adds the tests their survivors named. It changes no source.

🛠️ How it works

Scope	Before	After	Target	Floor
tools-copilot (426 mutants)	82.39 (55 survived, 20 uncovered)	95.31 (19, 1)	≥ 90	80 → 93
tools-codex (381)	89.50 (38, 2)	96.33 (14, 0)	≥ 92	87 → 94
tools-opencode (283)	87.63 (34, 1)	96.82 (8, 1)	≥ 90	81 → 94

• Tests under cli/tests/contexts/tools/domain/profiles/. They cover each profile's path mapping, build contract, the codex agent TOML and transcript location, and the opencode hooks bridge.
• 71 mutants were applied by hand, and each turned its test red. Example: codex build.ts:65 with >= turned into > fails "leaves a user's project_doc_max_bytes already at the floor untouched".
• Every score comes from run-mutation.mjs <scope> --force, before and after. Each floor is the measured score minus two, rounded down.

🧪 How to verify

git diff --stat origin/next... -- cli/src      # empty
cd cli && for s in tools-copilot tools-codex tools-opencode; do node scripts/run-mutation.mjs $s; done

Measured on this branch: 379 files and 5073 tests passed. Typecheck, lint, test:arch, knip and type honesty are clean.

⚠️ Heads-up

• The surviving mutants are equivalent. Most are section-prefix regexes whose callers always pass a path that already starts with the section. A few are the known stryker artefact of a capability constructor that throws at import.
• One piece of dead code turned up and is left for its own issue: commandsHandler.convertFrontmatter in the copilot profile.

🔗 Linked issue

Refs #799. With #815 and #819 this covers every scope #799 names, so it closes once all three are merged.

✅ I certify

• I have read the contributing guide and followed the PR template.
• Tests were written red first and every gate listed above passed locally.

🤖 Generated with Claude Code

https://claude.ai/code/session_011x4ms5qcGuZgYhCxfdHMUb