docs: add OpenChamber feature docs and translations (#1400)

* docs: add OpenChamber feature docs and translations

Add 30 new docs pages covering OpenChamber-specific workflows and setup:
OpenCode server, providers/models/agents, MCP, skills, commands & snippets,
usage, projects, context, notes/todos/plans, scheduled tasks, project actions,
preview, worktrees, multi-run, git & GitHub, magic prompts, git identities,
mobile/PWA, security, notifications, voice, project icons, remote instances,
desktop browser, updates, and three troubleshooting pages.

Rebuild sidebar into eight task-oriented sections and translate every new
page into all six supported locales (uk, zh-cn, es, pt-br, ko, pl).

* docs: surface new sections on homepage and cross-link tunnels

Add an Explore block to the docs homepage (all seven locales) linking to
the new section anchors, and cross-link the Tunnels page to Security and
PWA & Mobile.

packages/docs/content/docs/index.mdx

@@ -20,6 +20,13 @@ Use these docs to:
 - [Tunnels](/tunnels/)
 - [Troubleshooting](/troubleshooting/)
 
+## Explore
+
+- [Projects](/projects/) and [Worktree Sessions](/worktrees/) — organize and isolate your work
+- [Providers, Models & Agents](/providers/) — connect OpenCode and pick a model
+- [Git & GitHub Workflows](/git/) — commit, review, and open PRs
+- [Security](/security/) and [Tunnels](/tunnels/) — protect and reach your instance
+
 ## What OpenChamber is for
 
 OpenChamber is for the parts of AI coding that benefit from a control room: branching sessions, reviewing diffs, managing terminals, watching tool progress, running project actions, and keeping the full board visible while the agent works.