skills: tri-pipeline fast path (t27b first, frontier --only seal reuse) and a t27o skill #10541

Goal

Owner, 2026-10-18 (translated): "use t27b, t27c seal to speed up, and save it in the skills". Put the fast path into the skill every spec task loads, and give t27o a skill of its own. Part of #10522.

Deliverable

• .claude/skills/tri-pipeline/SKILL.md: "One spec, end to end -- fast path first": t27b test for the inner loop, t27c frontier --only <specs> --list (seal-keyed REUSE) for specs that did not change, t27c test-report / tri test once as the final gate, the seal as the REUSE key; reuse release binaries instead of rebuilding; t27b's exit codes and which are a verdict; the sandbox ZIG cache trap; git add -f for gen files. Remove the stale "tri test does not yet fail on vacuous" (tri test: refuse vacuous passes -- report.t27 reads the "vacuous passes N of M" line (Closes #10497) #10507 landed).
• .claude/skills/t27o/SKILL.md: where t27o's truth lives, how to make a refusal class convertible and measure it, --check, the loop tick for [EPIC] t27o overnight loop: dogfood on the roadmap repos, t27b-fast checks, refusal classes, competitors (feeds #10486 M2) #10522, the traps met tonight.

Done when

python3 -I tools/check_documented_commands_exist.py prints ok with no new dead mention; both files ASCII only; every timing quoted carries its spec and date.

Boundary

• May touch: .claude/skills/tri-pipeline/SKILL.md, .claude/skills/t27o/SKILL.md (new).
• Must not touch: other skills (the analog loop owns analog-emulation).

Links

#10522, #10525, #10527.

User Scenarios

• Given a spec task loads the tri-pipeline skill, When the developer runs the fast path, Then t27b test executes for the inner loop, t27c frontier --only <specs> --list reuses seal-keyed results for unchanged specs, and t27c test-report / tri test runs once as the final gate.
• Given the t27o skill exists, When a developer invokes t27o with --check, Then the skill documents where t27o's truth lives, how to make a refusal class convertible and measure it, and the loop tick for [EPIC] t27o overnight loop: dogfood on the roadmap repos, t27b-fast checks, refusal classes, competitors (feeds #10486 M2) #10522.

Requirements

FR-001: The file .claude/skills/tri-pipeline/SKILL.md MUST contain the fast path procedure: t27b test for inner loop, t27c frontier --only <specs> --list for seal-keyed REUSE of unchanged specs, t27c test-report / tri test once as final gate, seal as REUSE key, reuse release binaries, t27b exit codes as verdict, sandbox ZIG cache trap, git add -f for gen files, and removal of stale "tri test does not yet fail on vacuous" note.
FR-002: The file .claude/skills/t27o/SKILL.md MUST be created and document where t27o's truth lives, how to make a refusal class convertible and measure it, --check usage, the loop tick for #10522, and traps encountered.
FR-003: Both skill files MUST be ASCII only.
FR-004: Every timing quoted in both skill files MUST carry its spec and date.
FR-005: Running python3 -I tools/check_documented_commands_exist.py MUST print ok with no new dead mention.