feat(search): unify session transcript search (#2877)

src/agent_loop.py

@@ -332,7 +332,7 @@ If the user asks for a reminder/alarm before the event, pass `reminder_minutes`
     "create_session": "- ```create_session``` — Create a new chat. Line 1 = chat name, line 2 = model name. Use for background/parallel work.",
     "list_sessions": "- ```list_sessions``` — List chats sorted MOST-RECENT FIRST (the UI calls them 'chats') with clickable chat-title links. Output includes a relative \"last active\" timestamp per row, so the first row is the user's most recent chat. Content = optional filter keyword (matches chat name). When answering, preserve the `[title](#session-id)` links exactly; do not convert them into plain text.",
     "send_to_session": "- ```send_to_session``` — Send a message to another session. Line 1 = session_id, rest = message. Use for orchestrating work across sessions.",
-    "search_chats": "- ```search_chats``` — Search across all chat history. Use when user asks 'did we discuss X?' or 'find the conversation about Y'.",
+    "search_chats": "- ```search_chats``` — Search past session transcripts for direct conversation evidence. Use when user asks 'did we discuss X?', 'find the conversation about Y', or when prior chat context is more appropriate than persistent memory.",
     "pipeline": "- ```pipeline``` — Run a multi-step AI pipeline. Args (JSON) with ordered steps, each specifying a model and prompt. Use for complex workflows.",
     "ui_control": "- ```ui_control``` — Control the UI: toggle tools on/off, OPEN PANELS, open email reply drafts, switch models, change themes. Commands: `toggle <name> on/off` (names: bash/shell, web/search, research, incognito, document_editor/documents), `open_panel <name>` (panels: documents, gallery, email, sessions, notes, memories/brain, skills, settings, cookbook), `open_email_reply <uid> <folder> <reply|reply-all|ai-reply>` (opens an email compose document, does NOT send), `set_mode agent/chat`, `switch_model <name>`, `set_theme <preset>`, `create_theme <name> <bg> <fg> <panel> <border> <accent>` (optional key=val for advanced colors AND background effects: bgPattern=<none|dots|synapse|rain|constellations|perlin-flow|petals|sparkles|embers>, bgEffectColor=#RRGGBB, bgEffectIntensity=<num>, bgEffectSize=<num>, frosted=true|false). \"open documents\" / \"open library\" / \"show gallery\" / \"open inbox\" / \"open notes\" / \"open cookbook\" all map to `open_panel <name>`. Theme presets: dark, light, midnight, paper, cyberpunk, retrowave, forest, ocean, ume, copper, terminal, organs, lavender, gpt, claude, cute.",
     "ask_user": "- ```ask_user``` — Ask the user a multiple-choice question when the task is genuinely ambiguous and the answer changes what you do next (pick an approach, confirm an assumption, choose a target). Args (JSON): {\"question\": \"...\", \"options\": [{\"label\": \"...\", \"description\": \"...\"?}, ...], \"multi\": false?}. 2-6 options. The user gets clickable buttons; calling this ENDS your turn and their choice comes back as your next message. Prefer sensible defaults — only ask when you truly can't proceed well without their input.",