feat(bitbucket): add guarded cloud PR merge

[KatalKavya96]

Summary

• Adds guarded Bitbucket Cloud pull-request merge support via magpie-bitbucket pr merge <id> --strategy {merge,squash,rebase}.
• Maps the Cloud merge path onto the change-request land(id, strategy) -> landed_ref contract shape, including extraction of the resulting merge commit when available.
• Keeps Bitbucket Data Center merge writes explicitly fail-closed and preserves queued/submitted merge state instead of reporting an incomplete merge as already landed.

Type of change

• Skill change (.claude/skills/<name>/) — eval fixtures updated below
• Tool / bridge contract (tools/<system>/*.md)
• Python package (tools/*/ with pyproject.toml)
• Groovy reference impl
• Cross-cutting (RFC, AGENTS.md, sandbox, privacy-LLM)
• Documentation (docs/, README.md, CONTRIBUTING.md)
• Project template (projects/_template/)
• CI / dev loop (prek, workflows, validators)
• Other:

Test plan

• prek run --all-files passes
• For Python packages touched: uv run pytest / ruff check / mypy passes
• For Groovy bridges touched: command-line invocation tested end-to-end
• For skill changes: eval suite passes for the affected skill
  (PYTHONPATH=tools/skill-evals/src python3 -m skill_evals.runner tools/skill-evals/evals/<skill>/)
• For skill behaviour changes: a new or updated eval fixture is included in this PR
  (a regression test for the bug fixed / the behaviour added — see CONTRIBUTING.md)
• Other:
  • focused merge tests cover strategy payload, completed merge normalization, queued merge normalization, landed_ref, Data Center fail-closed behavior, and CLI dispatch
  • full Bitbucket test suite passes
  • git diff --check passes
  • workspace pytest passes with a short macOS temp path to avoid the unrelated AF_UNIX pathname-length limitation

RFC-AI-0004 compliance

• HITL — the merge mutation remains gated on explicit caller-side user confirmation
• Sandbox — no new unrestricted host access; the implementation reuses the existing guarded HTTPS write path
• Vendor neutrality — the Bitbucket-specific command is mapped onto the generic change-request land contract rather than introducing a new framework-level vendor

[KatalKavya96]

Hi @potiuk — next narrow #606 follow-up after #1194.

This adds guarded Bitbucket Cloud pr merge <id> --strategy {merge,squash,rebase}, maps it onto the change-request land(id, strategy) -> landed_ref contract shape, preserves queued merge state, and keeps Data Center merge writes fail-closed.

Focused/full Bitbucket tests, Ruff, mypy, repository hooks, and workspace pytest are green.

Would appreciate your review when you get a chance.

[Kaap10]

Thanks for working on this @KatalKavya96!

The overall structure and Data Center fail-closed handling look solid. However, there are two discrepancies between the documented contract shape and the implementation:

1. Missing --strategy in CLI & Payload:

   • README.md and the PR summary document pr merge <id> --strategy {merge,squash,rebase}, but --strategy is missing from _build_parser() in cli.py.
   • cloud.merge_pull_request() currently hardcodes payload={"type": "pullrequest"} without accepting or mapping the strategy parameter to Bitbucket's API values (merge_commit, squash, fast_forward).

2. Missing landed_ref normalization:

   • The documentation mentions returning the merge commit as landed_ref when available, but in normalize.py (merged_pull_request), landed_ref is not extracted from result_data.get("merge_commit", {}).get("hash").

Could you add --strategy to cli.py / cloud.py and extract landed_ref in normalize.py along with matching tests?

[KatalKavya96]

Thanks @Kaap10

I updated the PR to:

• add required --strategy {merge,squash,rebase} CLI handling

• map those values to Bitbucket Cloud merge strategies

• pass the selected strategy through the merge request

• extract merge_commit.hash as landed_ref

• preserve queued merges without reporting a landed ref prematurely

• add matching strategy, normalization, CLI, and Data Center fail-closed tests

Thanks for catching the contract/implementation mismatch.