feat(cli): refresh the statusline ctx segment per settled provider request (#4545)

[me2seeks]

Closes #4545.

Problem

The TUI statusline ctx used/window pct% segment only moved once per turn, when the end-of-turn token_usage event landed. During a long agentic turn — dozens of tool steps over minutes, exactly when the context grows fastest — the indicator sat frozen at the previous turn's value, hiding the signal that says "time to /compact or wrap up".

Approach

Reuse the desktop inspector's pull model instead of growing a parallel push event (design + audit: docs/tui-live-ctx-updates.md, 中文讲解 docs/tui-live-ctx-updates.zh-CN.md):

• The Host already commits a latest-context snapshot at every settled provider request (provider-request-telemetry.ts), and context.diagnostics.query is a plain read with no busy gate — the desktop inspector refreshes from it mid-turn on trace-relevant events.
• New packages/cli/src/tui-context-refresh.ts: the desktop trace-relevant event set (tool_start, tool_result, token_usage, …) + a restart-on-event debouncer (400 ms, same as desktop) whose revision guard lets only the latest issued query apply; a failed read leaves the last value standing.
• pi-tui-runner.ts: observe() on the shared turn-drain onEvent (covers user-submitted and Host-attached turns alike) and on the resumeLatest loop; cancel() on teardown; a stale-session guard drops results that resolve after a switch. The query calls the driver directly — runControl's serial lock exists for mutations, and /context's mid-turn refusal is a TUI-local choice, not a protocol constraint.
• The apply path uses the same contextRemaining = contextWindow − inputTokens formula as the token_usage path (fix(runtime): emit contextRemaining in token_usage events so the TUI ctx segment renders #1067), derived from the same settled request — the two cannot disagree. Turn-end token_usage stays the authoritative persisted record; this only enriches the live turn.

Zero protocol / runtime / persistence changes: no new event type, no billing semantics touched (#972).

Non-goals

• Token-level updates during one streaming request: providers report input tokens only at completion, so exact mid-request values do not exist; the pre-dispatch bytes/4 estimate is too rough (base64 attachments) to show.
• Unlocking /context mid-turn over the same query path — a free follow-up, kept out to stay small.
• Desktop changes (already has this granularity).

Test plan

• New unit tests tui-context-refresh.test.ts (9): event-set parity with desktop, debounce coalescing, out-of-order resolution guard, failed read keeps last value, cancel retires scheduled + in-flight queries, real-timer sanity.
• New runner integration tests (2): ctx segment moves mid-turn while the turn is parked after tool_start (before any token_usage); a failing snapshot read leaves the segment untouched and silent.
• Full maka-agent package suite: 732 passed, 0 failed (3 pre-existing skips); whole-repo typecheck green; biome lint/format clean; ASF header check green.