Retire the agent-pr Bats suites where Go covers them #925

Problem

tests/skills/agent-pr/ holds the unattended wrapper Bats suites and their helper, and tests/skills/pr/test_helper.bash is shared by the pr suites. After children 10 and 13 the unattended behavior is in Go and the wrappers forward, so the wrapper suites mostly retest the shell. Once children 14 and 15 have removed the cases that used the shared helper, helper functions that nothing calls are dead weight.

Part of #588 and #323. Changes only the agent-pr suite files and, after children 14 and 15 are merged, the two helpers. No shell body or generated file changes.

Acceptance criteria

1. AC1: Given the agent-pr cases before the change, when the change lands, then a table in the pull request lists every case with its disposition: removed with the name of the Go test that covers it and the name of the retained frozen-path case that covers the same authority or refusal outcome of the frozen wrappers, or kept with the reason (including "frozen shell outcome with no other coverage: kept until the shell is removed").
2. AC2: Given each of the four agent-pr entry points, when the suite runs, then the argument contract of that entry point is still exercised once (the publication entry refuses --confirmed; the other entries forward their arguments), and no universal --confirmed refusal case is added.
3. AC3: Given a consumer with only agent-pr deployed and a binary that has the behavior, when the standalone case runs against a concrete changed fixture repository, then it passes and uses no file from the pr skill.
4. AC4: Given the frozen path with a binary lacking the behavior, when the suite runs, then one case per entry point remains, and no case is removed whose only coverage of a supported frozen-wrapper outcome (an authority refusal, an exit status, a message, a file written) is itself.
5. AC5: Given the agent-pr helper and tests/skills/pr/test_helper.bash, when the change lands, then each function no remaining case calls is removed, and no function a remaining case calls is removed.
6. AC6: Given the Bats jobs on Ubuntu and macOS, when they run on the merged head, then they pass.
7. AC7: Non-functional: the helper trim is made only after the pull requests of children 14 and 15 are merged, so the helper is never edited by two open pull requests.

Scope and non-goals

Scope: the agent-pr suites, the table of dispositions and the helper trim.

Non-goal: the pr workflow, compatibility, section and writer suites, which children 14 and 15 retire. Non-goal: changing any shell or generated file. This pull request deletes only Bats cases and unused test helper functions: no script, library or generated copy is removed, and no owner-tier path in .agents/agent-skills.conf is touched (those go to the single cutover issue under #588). Non-goal: removing cases with no Go counterpart or whose frozen-shell outcome has no other retained coverage.

Approach

Meet AC1 to AC7 by building the disposition table first, resolving each Go test name to an existing test from child 10, then removing covered cases, then trimming unused helper functions with a search for each function name across tests/.

Dependencies

Blocked by: #919, #922, #923, #924.

Size

M. One pull request, mostly deletions, under the code line limit.

Verify plan

• AC1: the disposition table in the pull request, checked row by row at review, including the frozen-path coverage column.
• AC2, AC4: the retained case list, the table's frozen-path coverage column and the passing Bats job.
• AC3: the standalone case with only agent-pr deployed, run on the merged head.
• AC5: a search for each removed helper function name returns no caller.
• AC6: the Bats jobs on Ubuntu and macOS on the merged head.
• AC7: the merge order of the pull requests of children 14, 15 and 16.
• 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

A removed helper function may be used by a suite outside the ones searched; AC5's search covers all of tests/. Undo: revert the change; cases and helpers return.

Operator authority

None.