fix(parallel-issues): support resumable artifact preparation

[thewrz]

This was written agentically; verify its assertions:

Why

Interrupted issue worktrees could not safely resume once fence artifacts existed, forcing manual deletion around potentially valuable uncommitted implementation work.

What

• Add an explicit artifact-resume path that archives the prior fenced set and regenerates it.
• Preserve and report untracked and modified implementation state during resume.
• Report resumable existing worktrees before refusing duplicate creation.
• Document the exact resume command and cover the workflow with fixtures.

Decisions

• Keep duplicate worktree creation fail-closed while surfacing deterministic resumability evidence.
• Archive only generated fencing artifacts under private evidence storage and leave every other worktree path untouched.
• Stacked on fix(parallel-issues): operator-named issues with stale In-progress status are dropped as active under --fast-mode #552 — merge that PR first. Agent-driven merges run chain-advance.sh --retarget --pr <this-PR> --base <default> and require its full proof before merging; interactive human merges may merge then delete the predecessor branch for GitHub's automatic retarget.

base=acb15ef8c748a62c0e2499743d95f629952a5aba
files=5
total.insertions=176
total.deletions=12
total.lines=188
operational.files=5
operational.insertions=176
operational.deletions=12
operational.lines=188
generated.files=0
generated.insertions=0
generated.deletions=0
generated.lines=0
lockfile.files=0
lockfile.insertions=0
lockfile.deletions=0
lockfile.lines=0
fixture.files=0
fixture.insertions=0
fixture.deletions=0
fixture.lines=0
non_operational.files=0
non_operational.insertions=0
non_operational.deletions=0
non_operational.lines=0

Testing

• Focused resume/worktree regressions — PASS
• tests/run-tests.sh — ALL GREEN
• Green log: /home/adam/github/agent-kit/.worktrees/feat/issue-545/.agent/logs/20260828T154425Z-test.log

🤖 Co-authored by Codex gpt-5.6-luna high.

Closes #545

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[thewrz]

This was written agentically; verify its assertions:

Adversarial review receipt

• Reviewer: provider=anthropic; model=claude-fable-5; effort=xhigh; mode=cross-provider (reason: User-authorized Claude Fable adversarial review)
• Counts: P1=0; P2=2; total=2
• Reviewed head: e189893
• Confirmed finding: Preserve prior-art file for resume command — verdict=fixed; fix commit SHA(s)=7733397d02dcc0a2c7fb2fc82a9e52fa4bb77371
• Confirmed finding: Fetch before resumability check — verdict=fixed; fix commit SHA(s)=7733397d02dcc0a2c7fb2fc82a9e52fa4bb77371

🤖 Co-authored by Codex.

[thewrz]

This was written agentically; verify its assertions:

Review ledger

Machine-readable record of every review already performed on this PR.

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  "pr": 559,
  "repo": "wrzonance/agent-kit",
  "reviews": [
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      "counts": {
        "p1": 0,
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      "reviewed_at": "2026-08-28T18:37:29Z"
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}

🤖 Co-authored by Codex.