feat: add French language mode (fr-lite/fr-full/fr-ultra)

[Cl3MM]

French language mode

Adds French as a new language variant, following the existing wenyan (Classical Chinese) pattern.

Before

Caveman only supports English (lite/full/ultra) and Classical Chinese (wenyan-lite/wenyan/wenyan-ultra) modes.

After

French speakers can use /caveman fr for telegraphic French with 3 intensity levels:

Example — "Why React component re-render?"

• fr-lite: "Le composant re-rend car nouvelle ref objet a chaque rendu. Envelopper avec useMemo."
• fr-full: "Nouvelle ref objet chaque rendu. Prop inline = nouvelle ref = re-rendu. useMemo."
• fr-ultra: "Prop inline → nouvelle ref → re-rendu. useMemo."

Example — "Explain database connection pooling."

• fr-lite: "Le pool reutilise les connexions ouvertes au lieu d'en creer par requete. Evite le cout du handshake."
• fr-full: "Pool reutilise connexions BDD ouvertes. Pas nouvelle connexion par requete. Evite handshake."
• fr-ultra: "Pool = reutilise conn BDD. Skip handshake → rapide sous charge."

Why

French is the 5th most spoken language worldwide. This follows the exact same pattern as wenyan — 3 intensity levels defined in the SKILL.md intensity table, modes registered in caveman-config.js, and command routing in caveman-mode-tracker.js.

Changes (5 files, 18 additions)

• skills/caveman/SKILL.md — intensity table rows + examples
• hooks/caveman-config.js — VALID_MODES list
• hooks/caveman-mode-tracker.js — /caveman fr command routing
• skills/caveman-help/SKILL.md — help card table
• commands/caveman.toml — description update

Synced copies (caveman/SKILL.md, .cursor/, .windsurf/, plugins/, caveman.skill) left untouched per CONTRIBUTING.md — CI handles sync after merge.