Spell the TU-promotion metavariable as <Class>, unbreaking main's references gate

[andrewboudreau]

Main is currently red on dead references at b6da5063f. This fixes it.

What broke

#2007 landed prose in tools/tiers_ratchet.py (3 sites) and notes/converted-tier.md (1 site) that names src/actors/X.cpp as a stand-in for "whichever file the TU promotion absorbed the symbols into".

check_dead_references reads every repo-rooted path appearing in prose as a real reference, so it read the stand-in as a rename that failed to carry into the prose:

FAIL: 2 prose reference(s) name a path that does not exist:
  notes/converted-tier.md
      names `src/actors/X.cpp`, which is not in the tree
  tools/tiers_ratchet.py
      names `src/actors/X.cpp`, which is not in the tree

Every PR cut from main after b6da5063f inherits this red. It is not those PRs' fault and it should not be resolved in those PRs.

The fix, and why not the baseline

Spelled src/actors/<Class>.cpp. GLOBBY in check_dead_references.py:93 already skips any reference containing <>, so the gate stops reading it as a path — and a metavariable is what the sentence meant in the first place.

This is deliberately not check_dead_references.py --update. The escape hatch is for references that are genuinely historical or belong to another repo; this one is neither. It is prose that should be clearer, so it got clearer. Suppressing it would also have left the next reader thinking src/actors/X.cpp was a real file.

The sibling stand-in in the same paragraphs, src/_ZN....cpp, has always been skipped because GLOBBY also matches .... This makes the two consistent — previously one placeholder was invisible to the gate and the other was fatal to it, for no reason a reader could see.

The src/actors/X.cpp literals in tools/test_tiers.py are untouched: they are fixture values in code, not prose, and the gate never read them.

Verification

check_dead_references        no new dead references   (133 unresolved, was 135)
pytest tools/test_tiers.py   29 passed
tiers_ratchet --check        PASS   baseline 2567   current 2567
port_refcheck                405 checked, all resolve
check_src_tu_compiles        88/88

Docs/tooling-prose only. No source file, no delinks entry, no symbol, no byte.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WdCK1xgrJdiJzPCh3bAJfQ

[tangos-validator]

✅ PR validation — Passed

noverify: no source/build-data changes in this PR

_{Each changed src/*.c|*.cpp is compiled and its relocated bytes compared to the binary data on a private build box. Passing requires every changed file to reproduce the ROM byte-for-byte with correct relocation targets — this catches WRONG-DEST relocations and non-reproducing near-misses that ledger-scoped linkcheck skips.}