chore: update platform count in user-facing copy to 600+

[moekatib]

What

The CLI tells users it connects to 400+ platforms. The live count is 606 (api.withone.ai/open/count/platforms). Two spots were staler still, at 200+.

This updates 13 strings to 600+. Copy only, no behavior change.

Where it showed

File	Surface
src/cli.ts	one --help description + platforms hint
src/commands/init.ts	post-install banner, platform picker label (was 200+)
src/commands/login.ts	post-login banner
src/commands/onboard.ts	onboarding copy and the CLAUDE.md block written into user projects
src/lib/guide-content.ts	one guide
skills/one/SKILL.md	skill shipped to user projects
README.md	intro, one platforms section (was 200+)

The onboard and skill strings matter most: they get written into user projects, so the stale number propagates into agent context.

Note on the 200+ instances

A grep for 400+ alone misses them. Worth grepping [0-9]+\+ platforms rather than a specific number next time this is refreshed.

Verification

• npm run build and npm run typecheck clean
• Built binary checked: one --help prints 600+ on both lines
• npm test 385 pass / 6 fail, and the same 6 (resolveConfig) fail identically on a clean origin/main checkout, so they are pre-existing and unrelated
• Not published to npm, per the team's release flow

Left alone deliberately: Connect 2+ platforms to unlock cross-platform workflows in the guide, which is a real threshold and not a catalog count.

🤖 Generated with Claude Code