feat(agents): add thinking time logging between tool calls (#244)

* feat(agents): add thinking time logging between tool calls

Adds a ThinkingTimer utility that tracks the gap between tool results and
the next tool call. When the gap exceeds 3 seconds, it logs the duration
with a stopwatch emoji (⏱️ 4.2s).

Uses performance.now() for high-resolution timing and Intl.NumberFormat
for rendering duration in seconds with optional fraction digits.

Integrated across all 5 agents: Claude, Codex, Cursor, Gemini, OpenCode.

Closes #127

* fix: adjusting tests for mocking performance.now.

* fix: reducing diff for claude.

* fix: rm unused args for claude.

* rm unused args for codex.

* fix: rm unused args for gemini.

* fix: rm unused args for opencode.

* mv THINKING_THRESHOLD.

* rev: I decided to pospone node:perf_hooks integration since it requires more comprehensive refactoring.

* fix: using Intl unit formatting.

* tests for ThinkingTimer.

* fix: narrow unit.

* fix: making durationFormatter a class instance property since using one agent per run.

* fix: inverting condition in markToolCall.

* thinking timer improvements and fix actions/checkout v6 auth

- thinking timer: use » chevron and "thought for X seconds" format
- thinking timer: add debug timestamps for sanity checking
- demote PID namespace isolation logs to debug
- remove redundant "setting up git authentication" log
- fix duplicate Authorization header with actions/checkout v6: clean up
  includeIf credential entries that v6 persists via external config files

Co-authored-by: Cursor <cursoragent@cursor.com>

* standardize tool call log prefix to » double chevron

Co-authored-by: Cursor <cursoragent@cursor.com>

* update timer tests for new thinking log format

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: pullfrog[bot] <226033991+pullfrog[bot]@users.noreply.github.com>
Co-authored-by: Robin Tail <robin_tail@me.com>
Co-authored-by: Colin McDonnell <colinmcd94@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

utils/timer.ts

@@ -18,3 +18,32 @@ export class Timer {
     this.lastCheckpointTimestamp = now;
   }
 }
+
+const THINKING_THRESHOLD = 3000; // ms
+
+export class ThinkingTimer {
+  private readonly durationFormatter = new Intl.NumberFormat("en-US", {
+    style: "unit",
+    unit: "second",
+    unitDisplay: "long",
+    minimumFractionDigits: 0,
+    maximumFractionDigits: 1,
+  });
+
+  private lastToolResultTimestamp: number | null = null;
+
+  markToolResult(): void {
+    this.lastToolResultTimestamp = Date.now();
+    log.debug(`» thinking timer: markToolResult at ${this.lastToolResultTimestamp}`);
+  }
+
+  markToolCall(): void {
+    const now = Date.now();
+    log.debug(`» thinking timer: markToolCall at ${now}, lastToolResult=${this.lastToolResultTimestamp}`);
+    if (this.lastToolResultTimestamp === null) return;
+    const elapsed = now - this.lastToolResultTimestamp;
+    if (elapsed < THINKING_THRESHOLD) return;
+    const seconds = elapsed / 1000;
+    log.info(`» thought for ${this.durationFormatter.format(seconds)}`);
+  }
+}