feat: first-class session search and recall

[furukama]

Summary

HybridClaw already stores canonical session history, compacts older turns into semantic memory, and can export sessions, but it does not have a first-class user-facing way to search past conversations and pull relevant past context back into the current turn.

Why

This is one of the highest-leverage missing features for a multi-channel personal agent. Users need to be able to find old conversations, inspect the matching turn or session, and explicitly recall that material into the active session without manual export/import work.

Proposed scope

• Add a user-facing session search surface in TUI, web chat, and gateway commands.
• Support both keyword search and semantic search over older compacted memory.
• Return session id, channel/source, timestamp, short preview, and match reason.
• Add a recall action that injects a selected past turn/session summary into the current turn as explicit retrieved context.
• Keep recall operator-controlled and visible in the prompt/audit trail.

Candidate UX

• /session search <query> or !claw session search <query>
• /session recall <sessionId>
• web chat search panel with a "Use in this chat" action
• optional @session:<id> inline context reference

Implementation notes

• Build on existing session persistence, compaction, and semantic memory instead of introducing a parallel memory store.
• Preserve source attribution for recalled material.
• Avoid silently expanding prompts with old content; recall should be explicit.
• Respect channel/session privacy boundaries when exposing search results.

Acceptance criteria

• Users can search past sessions from at least one interactive surface.
• Search results include enough metadata to identify the right conversation.
• Users can pull a selected result into the current turn in a structured, auditable way.
• Recalled context is clearly marked in transcripts and does not mutate original history.
• Tests cover search matching, permission/boundary behavior, and recall prompt injection.