feature - add session-scoped MCP tool selection to TUI

[lgarceau768]

Summary

• Intercepts the first message submit on new sessions to show a searchable tool selection dialog when MCP servers are active, letting users choose which tools (and their token overhead) to include for the session
• Tool selection is persisted as a `Permission.Ruleset` deny list on the session, filtering unselected tools from every LLM call for its lifetime
• Adds a `session.tools` command palette entry for mid-session tool adjustment

Changes

• `src/mcp/index.ts` — add `defs()` to `MCP.Interface`, exposing the in-memory `Record<string, MCPToolDef[]>` cache
• `src/server/routes/instance/mcp.ts` — new `GET /mcp/tools` endpoint returning tools grouped by server with per-tool token estimates (`~chars/3.5`)
• `packages/sdk/js` — SDK regenerated; `sdk.client.mcp.tools()` and `session.update({ permission })` now available in v2 client
• `context/local.tsx` — `sessionTools` state: filter, pending prompt stash, resume callback, reset
• `component/dialog-session-tools.tsx` — new searchable dialog: tools grouped by MCP server, checkbox toggle, `[space]` toggle / `[a]` all / `[n]` none / `[enter]` confirm, live token count in title
• `component/prompt/index.tsx` — intercept first submit when MCP connected and pending is null; apply deny rules via `session.update` post-create; resume via stored callback after dialog closes
• `app.tsx` — `session.tools` command in Agent palette; mid-session mode passes current `sessionID` and writes updated rules on confirm
• `test/session/prompt-effect.test.ts`, `snapshot-tool-race.test.ts` — add `defs` to MCP mock objects

Test Plan

• Start TUI with at least one MCP server connected
• Type a message and press Enter — tool selection dialog should appear listing all tools grouped by server with token estimates
• Toggle individual tools with Space, select all with `a`, none with `n`, confirm with Enter
• Verify session is created and unselected tools are absent from subsequent LLM calls
• Press Esc — session should start with all tools (no filter applied)
• Open command palette mid-session and run `session.tools` — dialog pre-checks currently-enabled tools; confirm updates the session permission ruleset
• `bun typecheck` passes with zero errors

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Hey! Your PR title feature - add session-scoped MCP tool selection to TUI doesn't follow conventional commit format.

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[lgarceau768]

Tested and did not work :(

• needs more interation

[lgarceau768]

after modifications, the model opens, a little buggy as return collapses and closes the dialog need to remove this.

[lgarceau768]

also blocks the session from beginning until all mcps has loaded - with a failing mcp this is a little annoying

[lgarceau768]

if the user escapes the dialog and presses enter we assume the default? May not be the best path