fix(hooks): differentiate burst and edit-ratio heuristics on tool type

The burst counter incremented on any tool call <30s apart regardless of
tool type, so a bulk read of many files produced the same "Rapid-fire"
alert as a rapid-fire editing sequence. The edit-ratio check reported
"possible stuck/spiral" for any session under 10% edits past 30 minutes,
which a read-heavy analysis session satisfies structurally whether or not
the work is productive. Both mechanisms are confirmed in
docs/BRIEF-vurdering-v2.md, verification points 1a and 1b.

tool-tracker.mjs now tracks whether the current burst run consists only
of read tools and suppresses the rapid-fire alert for such runs. A
read-dominant session (>=70% reads) reports its low edit ratio as
context rather than as a stuck/spiral claim, and never as the sole
reason for a warning. Bursts involving Edit/Write/Bash and
non-read-dominant sessions behave exactly as before.

No new data is recorded: the differentiation uses tool_name, which
events.jsonl already logs. The privacy design is untouched.

Tests first (Iron Law): 5 cases in tests/tool-tracker.test.mjs, 3 of
which failed against the previous implementation, 2 of which are
regression guards that passed before and still pass.

Verified: node --test tests/*.test.mjs -> 263 pass, 5 fail. All 5
failures are the perf wall-clock assertions, which fail identically on
HEAD without this change (measured by stashing and re-running) — they
are a pre-existing property of this machine, not a regression.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011wMhJuPFUiWqKLSQjrzCXP

tests/tool-tracker.test.mjs

@@ -93,3 +93,75 @@ describe('tool-tracker', () => {
     assert.equal(out.continue, true);
   });
 });
+
+// Tiltak 1 (BRIEF-vurdering-v2.md): burst and edit-ratio heuristics must
+// differentiate on tool type. A bulk-read sequence is structurally
+// indistinguishable from a rapid-fire editing sequence today.
+describe('tool-tracker — task-type calibration', () => {
+  it('does not raise a rapid-fire alert for a pure read burst', () => {
+    dir = setupTestDir();
+    // burst_count 9 + this call = THRESHOLD_HARD_BURST (10), all reads
+    createStateFile(dir, 'b1', freshState({
+      last_event_epoch: Math.floor(Date.now() / 1000) - 5,
+      burst_count: 9,
+      tool_count: 30,
+      read_count: 30,
+    }));
+    const out = runHook('tool-tracker.mjs', { session_id: 'b1', tool_name: 'Read' }, dir);
+    const ctx = out.hookSpecificOutput?.additionalContext || '';
+    assert.ok(!ctx.includes('Rapid-fire'), `expected no rapid-fire alert, got: ${ctx}`);
+    assert.equal(out.continue, true);
+  });
+
+  it('still raises a rapid-fire alert when the burst includes an edit', () => {
+    dir = setupTestDir();
+    createStateFile(dir, 'b2', freshState({
+      last_event_epoch: Math.floor(Date.now() / 1000) - 5,
+      burst_count: 9,
+      tool_count: 30,
+      read_count: 29,
+    }));
+    const out = runHook('tool-tracker.mjs', { session_id: 'b2', tool_name: 'Edit' }, dir);
+    const ctx = out.hookSpecificOutput?.additionalContext || '';
+    assert.ok(ctx.includes('Rapid-fire'), `expected rapid-fire alert, got: ${ctx}`);
+  });
+
+  it('does not call a read-dominant session stuck/spiral', () => {
+    dir = setupTestDir();
+    // 40 min, 50 tool calls, no edits, all reads — a research/audit session
+    createStateFile(dir, 'e1', freshState({
+      start_epoch: Math.floor(Date.now() / 1000) - 40 * 60,
+      tool_count: 49,
+      edit_count: 0,
+      read_count: 49,
+    }));
+    const out = runHook('tool-tracker.mjs', { session_id: 'e1', tool_name: 'Read' }, dir);
+    const ctx = out.hookSpecificOutput?.additionalContext || '';
+    assert.ok(!ctx.includes('stuck/spiral'), `expected no stuck/spiral claim, got: ${ctx}`);
+  });
+
+  it('still reports low edit ratio when the session is not read-dominant', () => {
+    dir = setupTestDir();
+    // Same duration and volume, but reads are a minority (5/50)
+    createStateFile(dir, 'e2', freshState({
+      start_epoch: Math.floor(Date.now() / 1000) - 40 * 60,
+      tool_count: 49,
+      edit_count: 2,
+      read_count: 5,
+    }));
+    const out = runHook('tool-tracker.mjs', { session_id: 'e2', tool_name: 'Bash' }, dir);
+    const ctx = out.hookSpecificOutput?.additionalContext || '';
+    assert.ok(ctx.includes('stuck/spiral'), `expected stuck/spiral claim, got: ${ctx}`);
+  });
+
+  it('counts read tools in read_count and leaves it alone for others', () => {
+    dir = setupTestDir();
+    createStateFile(dir, 'r1', freshState());
+    runHook('tool-tracker.mjs', { session_id: 'r1', tool_name: 'Grep' }, dir);
+    assert.equal(readState(dir, 'r1').read_count, 1);
+    runHook('tool-tracker.mjs', { session_id: 'r1', tool_name: 'Glob' }, dir);
+    assert.equal(readState(dir, 'r1').read_count, 2);
+    runHook('tool-tracker.mjs', { session_id: 'r1', tool_name: 'Write' }, dir);
+    assert.equal(readState(dir, 'r1').read_count, 2);
+  });
+});