Remove non-owner conflict shell and Python fallbacks after N-2 #909

Problem

The conflict classifier, union writer, side picker and Python helper retain 532 code lines across packages/agents/source/skills/resolve-rebase-conflicts/shared/scripts/classify-conflicts.sh:1, packages/agents/source/skills/resolve-rebase-conflicts/shared/scripts/resolve-union.sh:1, packages/agents/source/skills/resolve-rebase-conflicts/shared/scripts/take-side.sh:1 and packages/agents/source/skills/resolve-rebase-conflicts/shared/scripts/conflict_shape.py:1. Keeping only a partial helper after the workflow port would preserve a second implementation and its interpreter requirements indefinitely.

Part of #588 and #326.

Acceptance criteria

1. AC1: Given the removal release, when compatibility evidence is read, then all required conflict commands have completed their two-release warning period.
2. AC2: Given the three public conflict entry points and a supported binary, when invoked after removal, then they preserve the activated Go workflow contract.
3. AC3: Given generated deployments after removal, when implementations are inspected, then the assigned shell algorithms and Python helper are absent.
4. AC4: Given valid supported inputs with no Python or uv installed, when the migrated conflict workflow runs, then it completes through Go and Git.
5. AC5: Given the helper's former internal mode interface, when the retirement ledger is read, then all callers and tests are accounted for by replacement or the documented expired compatibility path.
6. AC6: Given the removed algorithms, when their coverage ledger is inspected, then their still-supported behavior has executing Go coverage.
7. AC7: Given the removal diff, when protected paths are classified, then no owner or constitutional path is changed or deleted.
8. AC8: Given regenerated packages and deployments, when consistency checks run, then they pass.
9. AC9: Non-functional: retained public shell entries perform only fixed forwarding through the shared launcher.

Scope and non-goals

Scope: only the four non-owner implementations, their generated copies, three fixed forwarding entries and Go integration adjustments.

Non-goal: Bats or Python test retirement, which must land separately in child 12. Non-goal: the resolve guard, rebase guards, shared libraries, the launcher, or automatic token application. The resolve guard and its protected copies remain for the single cutover under #588 with owner exact-head review. No new shell logic is permitted.

Approach

Use child 12's completed test-retirement ledger to remove implementations without losing the independent union proof or refusal/misuse/failure distinctions. Confirm the only implementation callers of the Python helper are the classifier and union workflow plus their frozen tests; record any consumer-facing helper usage before removing it. Remove obsolete interpreter prerequisites from skill prose only after their fallback is gone. Preserve base-side and replayed-side calling conventions. Regenerate the two packages and deployments from maintained sources.

Dependencies

Blocked by: #899, #900, #901, #902, #903, #904, #906, #333, #544, #753.

Prerequisites: #321's launcher and the completed N-2 window. This child does not wait on the owner cutover or change #328's guard implementation.

Size

M. Forecast 670 code lines: 532 measured implementation deletions, 30 fixed forwarding lines and 108 Go-integration/deployment adjustments. Prose allowance: 260 lines. Any copy retained outside the specified generated directories counts in full.

scc could not run in the isolated checkout. Measured baselines count non-blank lines other than full-line # comments, including Python docstrings and embedded code conservatively. Forecasts include implementation, tests, fixtures and registration; they are estimates, not measured future Go. Generated output is excluded only under packages/agents/claude/.apm/skills/, packages/agents/codex/.apm/skills/, .claude/skills/, .agents/skills/ and tokens.json. The source under packages/agents/source/ and copies anywhere else count. The final diff must be at most 800 code lines and 2,000 prose lines, with no exception; split before implementation if either forecast grows beyond its limit.

Verify plan

• AC1: inspect the command-bearing release and at least two subsequent warning releases.
• AC2, AC3, AC9: inspect retained forwarding paths and generated outputs; run classification, proven union, explicit side and refusal fixtures.
• AC4: run the native workflow with only its declared Go/Git runtime dependencies.
• AC5, AC6: search maintained and generated references; compare removed implementations/callers with child 12's ledger and executing Go coverage, and confirm no Bats or Python test retirement is included.
• AC7: classify every changed, renamed and deleted path against the pinned owner/constitutional patterns.
• AC8: regenerate, refresh tokens/deployments and lock records, then run generated-consistency and packaging checks.
• Definition of done: D1 each AC is verified at the merged head, with the commands and results cited in the pull request's Verification. D2 an independent review approves the exact merged head, and every finding has a recorded disposition. D3 required checks pass with no gate loosened. D4 the leak scans the repository specifies are clean, and every post made for this work passes the per-post leak review before it is posted. D5 every commit is signed. D6 the documentation matches the change or the Verification says why there is no impact. D7 every commit has an Assisted-by trailer and the pull request has the provenance:agent-assisted label. D8 the pull request stays within the size limits. D9 follow-ups are filed as issues and listed under Related. D10 the merge closes the issue through a closing reference, the board shows Done, and the final Status: comment names the merge commit.

Risks

An overlooked helper caller or premature interpreter removal can strand a fallback consumer. Weakening independent verification can stage data loss. Undo: revert removal and regenerate the exact frozen implementations and interpreter guidance.

Operator authority

None.