fix: remove remaining language attractor tokens

[Mariomarquezt]

Fixes #812.

Problem

710173f de-named the language rule in skills/caveman/SKILL.md to remove the Portuguese/Spanish example tokens that were pulling generation into the wrong language. Two other injected copies of the same rule were not touched and still carry the tokens on main:

File	Injected when
skills/caveman-help/SKILL.md:41	/caveman-help is invoked — the site identified in #812
src/hooks/caveman-activate.js:154	SessionStart, on a standalone hook install where SKILL.md is not found

The second one is not mentioned in the report. It is the fallback ruleset, and it is injected at SessionStart exactly like the file 710173f fixed, so it reproduces the same drift for that install path.

Change

Both rewordings follow the shape 710173f used: state the rule without naming any language, and make the "regardless of example text elsewhere" clause explicit.

-Keep user's language by default. User write Portuguese → reply Portuguese caveman.
+Keep user's language by default — reply in the language user writes, never switch
+regardless of example text or multilingual context elsewhere.

Scope notes

• caveman-help is not CI-mirrored under plugins/ (CONTRIBUTING, "not mirrored by CI" table), so the top-level source is the only copy. No sync gap to chase.
• README.md:137 also names the languages, but it is prose documentation and is never injected into a session, so it is left alone.
• No behaviour change beyond the rule text; no test asserted on the removed strings.

Verification

Full CI suite run locally on this branch:

• npm test — 125 passed, 0 failed
• tests/test_*.js — 169 passed, 0 failed across 8 files
• python -m unittest discover -s tests — Ran 58 tests, OK