fix(chains): publish complete predecessor joins before dispatch

[thewrz]

This was written agentically; verify its assertions:

Why

A join could start with only one required predecessor, silently dropping selected work or using an incomplete base.

What

Persist each predecessor’s initial publication identity and consume the saved plan’s complete ordered predecessor set during setup. Assemble and publish every required input before implementation, preserve partial progress on resume, and hand merge conflicts to the existing sole-writer resolution workflow with combined-code validation.

The PR targets fix/issue-907 (#918). Its complete initial integration baseline is 6bd083371c0e8da19479e59a159fc3b545b664ac, which also includes initial #905 and #911. GitHub’s displayed comparison includes those inherited changes; the immutable adversarial review uses that complete baseline to isolate #910. Completed parent repairs are integrated once at finalization in 90063dced58c387577e86bd4ef8e65bd645da3b9, which passed the canonical full suite and final-head CI.

Testing

• Failing boundary regressions before implementation; complete-set ancestry, publication, conflict resolution, failed validation, and resume cases.
• Focused chain tests 178/178, size contracts, static gates, and generated-plugin rebuild.
• AGENT_TEST_JOBS=8 AGENT_TEST_TIMEOUT_SCALE=2 tests/run-tests.sh on clean 42c43c5c15b630ed98a920e5e33b967102b40346: ALL GREEN, exit 0; pushed remote matches.
• One adversarial review and findings disposition.
• Completed parent repairs integrated and final-head GitHub CI.

Closes #910

🤖 Co-authored by Codex.

[coderabbitai]

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[thewrz]

One authorized adversarial review completed using Anthropic Claude claude-opus-5, effort xhigh, with tools disabled. No second review was sent after repairs.

Immutable input: complete integration base 6bd083371c0e8da19479e59a159fc3b545b664ac, reviewed head 42c43c5c15b630ed98a920e5e33b967102b40346, diff SHA-256 b61b01f2624dc346bb245ed969caf2567e606ff422b45122f984d373349d4330.

Findings disposition:

• P1: repaired recorded-base resume to accept a reachable integration base after the published branch advances. Fresh publication still requires exact remote identity.
• P2: require the actual local checkout to contain the recorded base before implementation handoff. The reported deleted-branch scenario safely recreates from remote; the reproduced stale-local-branch case is now refused.
• P2: support a legitimate empty-tree merge through the existing protected worktree-commit.sh --allow-empty --allow-base-inherited contract. Both parents remain ancestors; no direct-commit bypass.

Regression: six failures before repair; create-worktree 112/112 after repair. Finalized parents #907, #905 and #911 are integrated. Final head 90063dced58c387577e86bd4ef8e65bd645da3b9 passed AGENT_TEST_JOBS=8 AGENT_TEST_TIMEOUT_SCALE=2 tests/run-tests.sh: 152 suites, exit 0, ALL GREEN. Log .worktrees/fix/issue-910/.agent/logs/issue-910-final-full-90063dc.log, SHA-256 158f03d6d4f5e777c7ae9c591667d69846ec7682dd1632c740455a95bca66cd9. Required final-head CI, all four shards and aggregate gates are green. Generated plugin rebuilt. The PR remains draft.