Documented t27c subcommands exist: dead tri mentions fell 140 -> 138 on master after #10500; lower MAX_DEAD_TRI #10513

Goal

#10500 removed two dead tri mentions from .claude/skills/tri-pipeline.md (tri verify, tri experience query), so the equality ratchet in tools/check_documented_commands_exist.py now reads 138 against MAX_DEAD_TRI = 140 and the check "Documented t27c subcommands exist" fails on master (e25345f) and on every PR after it ("FAIL: dead tri mentions fell 140 -> 138 ... lower MAX_DEAD_TRI in the same commit"). #10500 should have lowered the constant itself.

Boundary

• tools/check_documented_commands_exist.py: MAX_DEAD_TRI = 140 -> 138. One constant inside an existing gate tool listed in tools/policy/foreign-exceptions.txt (same pattern as the PR claw: drift audit law as .t27 spec lowered by gen-c (T2-T3, Refs #9271) #9277 entry: a one-constant ratchet move, not new logic).

Scenarios

• Given master with the constant lowered, When the check runs, Then it passes with 138 dead mentions.

Requirements

• FR-001: The ceiling MUST equal the measured count, as the ratchet requires.

Success Criteria

• python3 tools/check_documented_commands_exist.py exits 0 on the PR head.
• The check "Documented t27c subcommands exist" is green on the PR.