HOK-1599: Fix needs-triage filtering, dedupe, and newline formatting

[timogilvie]

Summary

• Filter blocked-only items from Needs Triage: Issues that appear in the triage list solely because they are blocked by an external task (outside the selected set) are no longer surfaced as needing triage — being blocked is a dependency state, not a triage decision
• Fix duplicate display bug: Added a rendered_ids associative array (case-insensitive) so each task ID is only rendered once across all sections, preventing the same issue from appearing multiple times
• Fix items appearing on the same line: Replaced section_body+=$(printf ...) with section_body+="$(printf ...)"$'\n' — the subshell form strips trailing newlines, causing items to concatenate onto one line

Changes

• shared/lib/plan-queue-utils.ts — Updated buildQueuePlan to filter unknown_endpoint/depends_on triage records where the blocking task is external; promotes those external blockers into the queue plan's ancestor list instead
• shared/lib/wavemill-mill.sh — Added rendered_ids deduplication guard and fixed newline concatenation in render_grouped_task_list for all four display sections (available now, queued, conflict clusters, needs triage)
• tests/task-selection-renderer.test.sh — Tests updated to cover the new filtering and deduplication behavior
• tools/plan-queue.test.ts — Unit tests updated for the updated buildQueuePlan logic

Test plan

• Unit tests in tools/plan-queue.test.ts cover the external-blocker filtering logic
• Shell tests in tests/task-selection-renderer.test.sh cover deduplication and newline formatting
• Manual scenario: an issue blocked only by an external task no longer appears in Needs Triage; it moves to "Queued After Dependencies" with the external blocker listed

Self-review

Review tool exited with code 2 (transient Claude CLI failure — claude CLI exited with code 1). Tool and base branch confirmed present; failure is an infrastructure issue unrelated to the diff.

[timogilvie]

Wavemill Merge failed

GraphQL: 3 of 3 required status checks are expected. (mergePullRequest)