Merge origin/master and integrate environment selection

Co-Authored-By: Paperclip <noreply@paperclip.ing>

doc/SPEC-implementation.md

@@ -2129,3 +2129,7 @@ Chat connection and destination settings may supply project/workspace defaults.
 Agents inspect/select workspaces and request contained repository preparation through ordinary authorized APIs. Repository preparation is idempotent and may require the next admission; it never claims a host-only clone is available in an already-running remote session. Simultaneous tasks may still explicitly share one physical local/SSH folder. Remote sharing requires actual placement and coherent persistence capability.
 
 See [the layer architecture](plans/2026-10-09-task-workspaces.md) for resolution rules, module ownership, persistence versions, rollout, and verification.
+
+## Company fast-response service
+
+Companies may configure an optional shared API connection and model for short acknowledgements of accepted human turns. Fast responses use direct SDK inference alongside normal agent work, with a three-second admission deadline, bounded prompts/output, current authorization and independent `fast_response` accounting. They are server-marked platform receipts attributed to the agent, never completion, interaction or recovery evidence. Company-sponsored unlinked external senders are explicit; linked-user permission denials are never bypassed. See [fast-responses.md](fast-responses.md) for provider, delivery, history and endpoint contracts.