Make PTY capture store a prose summary and the harness's own session id #3454

Overview

ADR-061 §7 says a terminal (PTY) chat's summary is the cross-device artefact: locally derived prose with ANSI stripped, not raw output. §6 says its session id names the harness's own state (~/.claude/…, ~/.codex/sessions/…), marked local_only. Capture currently does neither.

Problem Statement

• The summary is raw output. SessionCapture::summary() (packages/agent/src/pty/capture.rs) returns the first 500 bytes of the raw transcript (SUMMARY_MAX_BYTES), including ANSI escapes and TUI repaints. Once a long session overflows the 1 MiB ring buffer, those bytes are an arbitrary mid-session fragment. The summary isn't local_only, so it's the one piece of raw scrollback allowed to leave the device, which ADR-061 §7 rules out.
• The stored id isn't resumable. Capture stores the daemon's PTY session id (session.id, packages/daemon/src/services/capture_service.rs). It can re-attach to a live terminal, but a harness can't resume from it.

Proposed Solution

1. Summary: strip ANSI and terminal control sequences from the transcript, then derive a short prose summary locally. Use the native model when it's available. When no summarizer is available, store no summary, which is ADR-061 §7's metadata-only fallback, rather than raw bytes.
2. Session id: record the harness's own resumable session id for the harnesses that expose one (Claude Code, Codex), discovered from the harness's session store after it exits, as a local_only field of ai-chat-pty. Keep the daemon PTY id only if re-attaching to a live session needs it after restart; otherwise drop it.
3. Both fields are written through the validated update (see Split ai-chat into an abstract base with ai-chat-native and ai-chat-pty subtypes #3446).

Architecture Impact

Brings the code in line with ADR-061 §6 and §7 (decisions/061-ai-chat-private-by-default-and-machine-bound-properties.md) and ADR-088 (ai-chat-pty fields). No ADR change. The resume feature itself (relaunching a harness with its resume flag, and a Resume button) is separate work.

Acceptance Criteria

• Follows development/node-type-sequence.md; the ai-chat-pty sheet in components/node-types.md stays accurate
• A stored summary contains no ANSI or control sequences and is prose, or is absent (tests with a transcript that has escapes, and one that overflowed the buffer)
• For Claude Code and Codex sessions, the harness's resumable session id is stored local_only (tests with fixture session stores)
• bun run test:changed passes; bun run quality:fix clean

Technical Specifications

Reference Files

• packages/agent/src/pty/capture.rs (SessionCapture, summary, transcript)
• packages/daemon/src/services/capture_service.rs (build_capture_properties, finalize_capture)
• packages/daemon/src/services/agent_session_service.rs
• packages/desktop-app/src/lib/components/viewers/ai-chat-pty-session.svelte

Dependencies

• Split ai-chat into an abstract base with ai-chat-native and ai-chat-pty subtypes #3446 (ai-chat-pty fields and capture through the validated update)

Non-Goals

• Resuming a harness session from the UI
• Embedding summaries (future work under ADR-061 §4)