fix(retro): count polyglot test files and exclude vendored dirs

[genisis0x]

Problem

/retro Step 1 command 10 counts repository test files with a JS/TS-only glob and excludes only node_modules:

find . -name '*.test.*' -o -name '*.spec.*' -o -name '*_test.*' -o -name '*_spec.*' 2>/dev/null | grep -v node_modules | wc -l

Python's dominant convention is test_*.py, which none of those patterns match, so on a Python repo the test_health.total_test_files metric never reflects the real count. Step 13 persists it and Step 12 trends it, so the test-health trend line tracks noise. As #1999 notes, a naive widening over-corrects, because virtualenv / vendored dependency trees (.venv, venv, site-packages, vendor) carry their own test suites and only node_modules was pruned.

Fix

• Add the common non-JS conventions: test_*.py and *Test.java. The existing *_test.* / *_spec.* already cover Go (*_test.go), Ruby (*_test.rb / *_spec.rb), and Python's *_test.py, so the genuine gaps are Python's test_ prefix and Java's separator-less FooTest.java.
• Prune vendored and virtualenv directories (node_modules, .venv, venv, site-packages, vendor, .git) inside find instead of post-filtering only node_modules, so dependency test suites no longer inflate the count.

Verification

On a polyglot fixture (5 real project test files across ts/js/go/py/java, plus dependency test files under .venv/ and node_modules/):

glob	count
old (JS-only, node_modules filter)	4 (misses test_*.py + *Test.java, counts a .venv test)
new	5 (exact project count)

bun test test/gen-skill-docs.test.ts test/skill-validation.test.ts — 734 pass, 0 fail. SKILL.md regenerated from the template.

The same glob shape also lives in the shared scripts/resolvers/testing.ts (the /ship before/after counts); left out of scope here to keep this focused on the /retro trend metric in #1999.

Closes #1999

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[jbetala7]

Heads-up on an overlap with #2037 (opened 06-18). Both PRs rewrite the same Step-1 test-counting glob — command 10 at retro/SKILL.md:1000 and the mirrored line in retro/SKILL.md.tmpl:

find . -name '*.test.*' -o -name '*.spec.*' -o -name '*_test.*' -o -name '*_spec.*' 2>/dev/null | grep -v node_modules | wc -l

— replacing the JS/TS-only glob + node_modules-only filter with a polyglot pattern and vendored-dir exclusion. Because both touch the identical lines in both SKILL.md and SKILL.md.tmpl, whichever merges second will conflict.

This PR is the narrower, issue-linked fix (Closes #1999, command 10 only). #2037 is effectively a superset: it also fixes the per-commit test glob in commands 12/13 (retro/SKILL.md:1009, still grep -E '\.(test|spec)\.' on main, which this PR doesn't touch) and adds a Step 1.5 anti-fabrication guard + regression test.

Not flagging either as wrong — just so the authors/maintainer can sequence them: if #2037 lands it subsumes this change (worth carrying Closes #1999 and crediting this PR); if this lands first, #2037 only needs to drop the now-duplicate command-10 hunk and keep its command-12/13 + plausibility-guard value.