Agent jobs (spawn_agents_on_csv) + progress UI (#10935)

## Summary
- Add agent job support: spawn a batch of sub-agents from CSV, auto-run,
auto-export, and store results in SQLite.
- Simplify workflow: remove run/resume/get-status/export tools; spawn is
deterministic and completes in one call.
- Improve exec UX: stable, single-line progress bar with ETA; suppress
sub-agent chatter in exec.

## Why
Enables map-reduce style workflows over arbitrarily large repos using
the existing Codex orchestrator. This addresses review feedback about
overly complex job controls and non-deterministic monitoring.

## Demo (progress bar)
```
./codex-rs/target/debug/codex exec \
  --enable collab \
  --enable sqlite \
  --full-auto \
  --progress-cursor \
  -c agents.max_threads=16 \
  -C /Users/daveaitel/code/codex \
  - <<'PROMPT'
Create /tmp/agent_job_progress_demo.csv with columns: path,area and 30 rows:
path = item-01..item-30, area = test.

Then call spawn_agents_on_csv with:
- csv_path: /tmp/agent_job_progress_demo.csv
- instruction: "Run `python - <<'PY'` to sleep a random 0.3–1.2s, then output JSON with keys: path, score (int). Set score = 1."
- output_csv_path: /tmp/agent_job_progress_demo_out.csv
PROMPT
```

## Review feedback addressed
- Auto-start jobs on spawn; removed run/resume/status/export tools.
- Auto-export on success.
- More descriptive tool spec + clearer prompts.
- Avoid deadlocks on spawn failure; pending/running handled safely.
- Progress bar no longer scrolls; stable single-line redraw.

## Tests
- `cd codex-rs && cargo test -p codex-exec`
- `cd codex-rs && cargo build -p codex-cli`

codex-rs/exec/src/cli.rs

@@ -86,6 +86,10 @@ pub struct Cli {
     #[arg(long = "color", value_enum, default_value_t = Color::Auto)]
     pub color: Color,
 
+    /// Force cursor-based progress updates in exec mode.
+    #[arg(long = "progress-cursor", default_value_t = false)]
+    pub progress_cursor: bool,
+
     /// Print events to stdout as JSONL.
     #[arg(
         long = "json",