Proposal: channel-native `/model` alias resolution and Feishu channel support

[chsimonpan]

We have been using ORG2 through external chat channels and found a few integration gaps that are worth upstreaming as a cohesive channel-layer improvement.

1. Channel /model should resolve aliases to the actual routed model id

In a channel context, users naturally type commands such as:

/model fable
/model gpt-5.5
/model sonnet

The channel handler should resolve those aliases the same way the rest of the app does, then persist/report the canonical routed model id (including provider/vendor slug when needed). Otherwise channel sessions can display one model, route another, or fail to map the command to a configured provider.

Implementation notes from our fork:

• c50ff795 — fix: handle channel model slash command
  • adds /model handling in channel slash flow
• b8a6204c — fix(agent-core): resolve channel model aliases to routed ids
  • normalizes aliases and chooses best candidate from available routed models
  • updates status-bar/reporting to show the resolved model consistently

This matters especially for provider-router setups where gpt-5.5 may map to openai/gpt-5.5:openai, or where Anthropic models require a vendor suffix for cache behavior.

2. Feishu / Lark channel support

We also added a Feishu channel integration for daily dogfooding. The useful pieces were:

• event parsing for Feishu direct/group messages
• media/image/file handling
• typing/reaction preservation across reinjection
• channel dispatch stability for external chat sessions
• channel session restoration in the sidebar/session loader

Relevant fork commits:

• a6562f6d — fix(feishu): handle media and typing reactions
• 3bf7a401 — fix(feishu): preserve typing reaction across reinject
• 3121ebbd — fix(channel): stabilize Feishu sessions and 150 dev runtime

Main touched areas:

• src-tauri/crates/agent-core/src/integrations/channels/feishu/*
• src-tauri/crates/agent-core/src/state/commands/channel_handler/*
• src-tauri/crates/agent-core/src/integrations/gateway/*
• session/sidebar restoration code for channel-backed sessions

Suggested split

This is probably best split into smaller upstream PRs:

1. Channel /model command + alias-to-routed-model resolution.
2. Feishu channel event parsing and send API.
3. Feishu media/typing reactions.
4. Channel session restoration/sidebar stability.

Happy to break out the clean pieces into PRs if Feishu/Lark support is in scope.