docs: Write Guides documentation (EN)

[100gle]

Parent Issue

Part of #2 — Phase 3: Documentation Content (EN)

Objective

Create the Guides section — practical how-to documentation for using Bub.

Source Material

• docs/channels/index.md: Channel overview, run modes, session semantics, debounce
• docs/channels/cli.md: CLI commands, syntax, options
• docs/channels/telegram.md: Telegram setup, access control
• docs/skills.md: Skill contract, discovery, authoring
• docs/deployment.md: Docker, operational checks, upgrade
• src/bub/builtin/tools.py: All 15+ builtin tools
• src/bub/skills.py: Skill discovery logic

Files to Create

1. src/content/docs/en/guides/channels.mdx

• What are channels (unified inbound pipeline)
• Builtin channels overview (CLI, Telegram)
• Session semantics per channel
• Outbound surfaces: send() vs on_event()
• Debounce behavior
• Adding custom channels (brief, link to extending section)

2. src/content/docs/en/guides/cli.mdx

• All CLI commands: bub chat, bub run, bub gateway, bub install, bub update, bub login, bub hooks
• Command options and flags
• Comma command mode (,help, ,skill, ,fs.read)
• Interactive features (auto-completion, Ctrl+X toggle, history)
• Session management (--session-id)

3. src/content/docs/en/guides/telegram.mdx

• Configuration: BUB_TELEGRAM_TOKEN, allowlists
• Message behavior and session IDs
• Access control (users, chats)
• Outbound delivery
• Proxy configuration

4. src/content/docs/en/guides/skills.mdx

• What are skills (SKILL.md documents)
• Skill anatomy: frontmatter + body + scripts + references
• Discovery roots and precedence (project > global > builtin)
• Authoring a new skill (step by step)
• Bundled skills: telegram, gh, skill-creator
• Progressive disclosure pattern

5. src/content/docs/en/guides/tools.mdx

• What are tools (builtin capabilities)
• All 15+ builtin tools reference table
• Tool categories: Shell/FS, Tape, Skills/Web, Meta
• Tool availability control (allowed_tools)
• Sub-agent tool and recursive filtering

6. src/content/docs/en/guides/deployment.mdx

• Prerequisites
• Three runtime modes (chat, gateway, run)
• Docker Compose setup (Dockerfile, docker-compose.yml, entrypoint.sh)
• Volume mounts and BUB_HOME
• Operational checks (5-step verification)
• Safe upgrade process

Acceptance Criteria

• All six files created with correct frontmatter and sidebar ordering
• Content migrated and enhanced from existing docs
• All CLI commands, tools, and config vars accurate
• Practical code examples included
• Links between guide pages work correctly

[100gle]

✅ Completed — en/guides/{channels,cli,telegram,skills,deployment}.mdx all migrated from docs/channels/, docs/skills.md, and docs/deployment.md. zh-cn mirrors created.