Closes #13606
Refs #13108

What does this PR do?
This is a follow-up to #13108.

In production, two issues were still reproducible:

• /docs/en could return 404
• English selection could be overridden by an existing non-English oc_locale

This PR fixes the remaining console-side docs routing/cookie sync gap by:

• handling /docs/<locale> as explicit locale input during request locale resolution
• canonicalizing /docs/en, /docs/en/, and /docs/en/* to English root docs paths
• appending Set-Cookie: oc_locale=<resolved-locale> on docs proxy responses

Changed files:

• packages/console/app/src/lib/language.ts
• packages/console/app/src/routes/docs/index.ts
• packages/console/app/src/routes/docs/[...path].ts
• packages/console/app/src/routes/s/[id].ts

Why this works:

• docs-path locale is now resolved before cookie/Accept-Language fallback
• English docs path is normalized to canonical root docs path
• locale cookie is synchronized on docs proxy responses, so English remains sticky

How did you verify your code works?

• Ran typecheck:
  • bun run typecheck (in packages/console/app)
• Ran targeted routing smoke checks:
  • docs("en", "/docs/en") -> /docs
  • docs("en", "/docs/en/") -> /docs/
  • docs("en", "/docs/en/agents") -> /docs/agents
• Ran locale-resolution precedence checks:
  • request to /docs/en with Cookie: oc_locale=ko resolves locale as en
  • request to /docs/en/agents with Accept-Language: ko resolves locale as en