feat: emit OSC 9 progress for reliable agent status detection (herdr integration)

Problem

Herdr currently detects jcode's agent state using only screen-scraping (TOML manifest regex/contains rules). This is fragile because:

1. Spinner frames change — ⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏ are matched per-frame, but any visual change breaks detection
2. Status text is version-dependent — "sending…", "thinking…", "running tool" labels change between jcode releases
3. False positives — generic words like "permission", "allow", "deny" appear in conversation text
4. No transcript viewer rule — scrollback text can confuse state detection
5. Stale text handling — requires complex bottom_non_empty_lines(N) + not gate tuning

How reliable agents do it

Every well-detected agent (codex, claude, opencode, kilo) uses OSC sequences as the primary detection path, with screen-scrape as a lower-priority fallback. jcode currently emits none.

Herdr captures two OSC channels from the terminal stream:

• OSC 0/2 (terminal title) → osc_title region in manifests
• OSC 9 (progress) → osc_progress region in manifests

Proposed solution

Emit structured OSC 9 progress sequences with a stable, version-independent payload when the TUI's ProcessingStatus changes:

Working:  ESC ] 9 ;jcode:working BEL
Idle:     ESC ] 9 ;jcode:idle BEL
Blocked:  ESC ] 9 ;jcode:blocked BEL

Implementation

• tui_lifecycle_runtime.rs — emit_agent_status_osc() method that writes the OSC 9 escape sequence to stdout, with dedup so it only emits on state transitions (safe to call on every redraw)
• run_shell.rs — call emit_agent_status_osc() on every completed spinner frame
• local.rs — call it when a turn finishes (→ idle)
• jcode-tui-permissions/src/lib.rs — emit jcode:blocked when the permissions viewer opens and jcode:idle when it closes (the main TUI is paused during permission prompts)
• app.rs / tui_lifecycle.rs — last_osc_state field for dedup tracking

Test coverage

Unit tests verify:

• Idle state when not processing
• Working state when processing
• Dedup skips repeated same-state calls
• State transitions emit correctly (working → idle → working)
• Suppressed in replay mode
• Suppressed when terminal title updates are off

Benefits

1. Version-stable — jcode:working string never changes even if UI text changes
2. No false positives — structured payload can't appear in conversation text
3. No stale text issues — OSC is a live signal, not screen-scraped
4. Cheap — one escape sequence per status change, negligible overhead
5. Backward compatible — screen-scrape rules remain as fallback
6. Consistent with ecosystem — matches codex/claude OSC-first approach

Reference branch

Changes available at: https://github.com/alecuba16/jcode/tree/herdr_detectable

Commit: acb185a3 — feat: emit OSC 9 progress for herdr agent status detection

Files changed (6 files, +172 lines)

crates/jcode-tui-permissions/src/lib.rs            |  21 +++
crates/jcode-tui/src/tui/app.rs                    |   2 +
crates/jcode-tui/src/tui/app/local.rs              |   1 +
crates/jcode-tui/src/tui/app/run_shell.rs          |   5 +
crates/jcode-tui/src/tui/app/tui_lifecycle.rs      |   2 +
crates/jcode-tui/src/tui/app/tui_lifecycle_runtime.rs | 141 +++++++++++

Start with crates/jcode-tui/src/tui/app/tui_lifecycle_runtime.rs and inspect the related changes in app.rs, tui_lifecycle.rs, run_shell.rs, local.rs, and jcode-tui-permissions/src/lib.rs. Run the relevant unit tests for status emission and confirm that OSC 9 transitions, deduplication, replay suppression, and terminal-title settings behave as described.