docs: fix broken documentation links in README and i18n (#1536)

* docs: fix broken documentation links in README and i18n

- Fix auto-combo.md → AUTO-COMBO.md case mismatch in README and all 32 i18n READMEs
- Add missing docs/features/context-relay.md English source (copied from i18n)
- Allowlist docs/features/ in .gitignore so the new file is tracked

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: add language switcher to context-relay.md English source

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/i18n/cs/README.md

@@ -2273,7 +2273,7 @@ Se não quiser criar credenciais próprias agora, ainda é possível usar o flux
 | [API Reference](docs/API_REFERENCE.md)                   | All endpoints with examples                         |
 | [MCP Server](open-sse/mcp-server/README.md)              | 25 MCP tools, IDE configs, Python/TS/Go clients     |
 | [A2A Server](src/lib/a2a/README.md)                      | JSON-RPC 2.0 protocol, skills, streaming, task mgmt |
-| [Auto-Combo Engine](docs/auto-combo.md)                  | 6-factor scoring, mode packs, self-healing          |
+| [Auto-Combo Engine](docs/AUTO-COMBO.md)                  | 6-factor scoring, mode packs, self-healing          |
 | [Context Relay](docs/features/context-relay.md)          | Session handoff strategy for account rotation       |
 | [Troubleshooting](docs/TROUBLESHOOTING.md)               | Common problems and solutions                       |
 | [Architecture](docs/ARCHITECTURE.md)                     | System architecture and internals                   |