Fork tasks from snapshots; snapshot only when text follows tool calls

TODO.md

@@ -4,8 +4,6 @@
 
 # M2 — Seeing the work
 
-- Forking from a snapshot
-  A new worktree from a snapshot commit plus a new agent session. Same vendor: the vendor's native session fork or resume. Different vendor: a handoff bundle from `export_context`, labelled in the UI as a handoff, not a true fork.
 - Terminals
   PTYs via `github.com/creack/pty`, rendered with xterm.js, one WebSocket per open terminal (the only WebSocket use in byre). Scoped to the task's worktree by default. Shown as a pane tab. Terminals don't survive a byre restart.
 - Per-project setup config
@@ -69,6 +67,7 @@
   An `export_context(purpose)` MCP tool producing a bundle with the goal, decisions made and why, current state, dead ends tried, open questions and relevant files. Used for cross-vendor forks, stage-to-stage handoff, and the durable record of a task. Compaction already writes the same contents.
 - Same-vendor forks
 - Cross-vendor handoffs
+  Forking a snapshot into a different vendor: the new session starts from a handoff bundle from `export_context` instead of the vendor's native fork, and the UI labels it a handoff, not a true fork. Same-vendor forks from a snapshot exist (see "Forking" in `docs/operations.md`).
 - Fork-and-compare
   A fan-out of N forks with different vendors or prompts from one snapshot, followed by a judge stage that produces a comparison with visuals.
 - Just-in-time fan-out with limits