bug(Prime(post-flight) prompt): explicit issue close step missing — kahuna-targeted MR auto-close doesn't fire

[bakeb7j0]

Summary

Issue auto-close (Closes #N) doesn't fire for kahuna-targeted MRs/PRs because the kahuna/<plan_id>-<slug> branch is not the protected base. The Prime(post-flight) prompt template needs an explicit glab issue close <X> (GitLab) / gh issue close <X> (GitHub) step to compensate.

The other agent reports: "was reliably done for wave-1/wave-2 but path-C cherry-pick missed it" — meaning the prompt template hasn't fully formalized the explicit-close step, so it leaks through path branches.

This is the same root issue tracked in mcp-server-sdlc#396 (wave_close_issue semantics — the tool name implies platform-close but only updates state.json), but at the Prime prompt layer rather than the MCP-tool layer. Two surfaces, same root cause.

Severity: low — caught by manual close pass at campaign close (see Plan #581 closeout), but every campaign still pays the hand-recovery cost.

Origin: Reported by sibling-campaign agent. @Scryer to expand and decide whether the fix lives in Prime prompt template alone, in wave_close_issue MCP tool (as platform-close), or both.

Implementation Steps

TBD — @Scryer to expand.

Test Procedures

TBD.

Acceptance Criteria

• Prime(post-flight) template includes explicit issue-close step that runs regardless of merge path (A/B/C cherry-pick branches)
• OR wave_close_issue MCP tool adds platform-close (per mcp-server-sdlc#396)
• Either way: post-merge issue state is closed without operator hand-close

Dependencies

• mcp-server-sdlc#396 (related — wave_close_issue platform-close)

Metadata

Severity: severity::minor (operator hand-recovery cost)
Origin: sibling-campaign tracker. @Scryer owns expansion.