attribute claude subagent log lines + per-session thinking timer; tighten lens calibration (#700)

* attribute claude subagent log lines + per-session thinking timer; tighten lens calibration

three orthogonal fixes diagnosed from the 10m PR-699 review run:

1. wire SessionLabeler into the Claude Code harness. claude-agent-sdk
   stamps every Assistant/User/System message with session_id and a
   non-null parent_tool_use_id when emitted from a subagent context, so
   the same FIFO labeler the OpenCode harness uses works here too.
   parallel reviewfrog dispatches now log with [lens:correctness] /
   [lens:operational-readiness] / etc. prefixes instead of being
   indistinguishable from the orchestrator. matches both "Task" and
   "Agent" tool names per the v2.1.63 rename.

2. one ThinkingTimer per session. the global timer treated cross-session
   interleaving (parent thinks → child tool_call, child returns →
   parent dispatches next) as parent thinking time, so individual
   "thought for Xs" numbers were untrustworthy. each session now owns
   its own timer and prefixes its own log line.

3. tighten the Review/IncrementalReview lens-add discipline. PR-699
   triggered 4 lenses on a typical refactor (no auth/billing/schema)
   when the prompt's own calibration says 2-3 is typical; the
   research-validated lens went deep on Resend idempotency window +
   prisma updateMany lost-updates without either being load-bearing.
   adds an explicit "name the failure mode this lens would catch
   that the diff plausibly introduces" bar, and tightens
   research-validated specifically: only when correctness depends on
   the third-party contract, not when the API is merely used.

side benefits from #1: subagents' TodoWrite events no longer clobber
the orchestrator's progress comment; subagent text no longer overwrites
finalOutput; system-event handler safely routes through eventLabel even
though SDK only emits system:init for the top-level query today.

* fix node strip-only mode: declare formatLine as field, not parameter property

* key claude subagent labels by parent_tool_use_id, not session_id

claude-agent-sdk runs subagents inside the orchestrator's session — they
share session_id — and stamps subagent messages with parent_tool_use_id
pointing at the Agent tool_use that spawned them. e2e on PR-700 with
preview-700-claude-labeling#1 confirmed the original session_id-keyed
wiring never differentiated subagent activity (only the dispatch line
got [lens:correctness] in the log; the subagent's reads, writes, and
todos all rendered as orchestrator).

extend SessionLabeler so labelFor accepts an optional parent_tool_use_id
and short-circuits to a direct map keyed by Agent tool_use id when set.
recordTaskDispatch optionally takes the Agent tool_use id (block.id at
dispatch time) and binds it. orchestrator events keep flowing through
the sessionID/FIFO path unchanged so opencode wiring is untouched.

* drop weak timer test that asserted only field isolation

per pullfrog review on PR-700: the 'two timers do not bleed timestamps'
test only verified that two ThinkingTimer instances have separate
private fields, which has always been true. doesn't earn its keep —
the per-session behavior is exercised by integration through claude.ts
+ opencode.ts.

agents/opencode.ts

@@ -377,7 +377,6 @@ type RunParams = {
 async function runOpenCode(params: RunParams): Promise<AgentResult> {
   const startTime = performance.now();
   let eventCount = 0;
-  const thinkingTimer = new ThinkingTimer();
 
   let finalOutput = "";
   let accumulatedTokens = { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 };
@@ -409,6 +408,23 @@ async function runOpenCode(params: RunParams): Promise<AgentResult> {
     return label === ORCHESTRATOR_LABEL ? message : formatWithLabel(label, message);
   }
 
+  // one ThinkingTimer per session — sharing a single timer across sessions
+  // conflated cross-session interleaving (parent thinks → child tool_call,
+  // or child returns → parent dispatches next) as parent thinking time. each
+  // timer formats its log lines through the session label so the "thought
+  // for X" attribution is visible in the merged stream.
+  const thinkingTimers = new Map<string, ThinkingTimer>();
+  function timerFor(label: string): ThinkingTimer {
+    let t = thinkingTimers.get(label);
+    if (!t) {
+      const formatLine = (line: string) =>
+        label === ORCHESTRATOR_LABEL ? line : formatWithLabel(label, line);
+      t = new ThinkingTimer(formatLine);
+      thinkingTimers.set(label, t);
+    }
+    return t;
+  }
+
   // tracks per-task dispatch metadata so the matching tool_result can log a
   // labeled "» subagent finished: lens=X duration=Ys" line. this is the most
   // useful per-lens observability available given that subagent-internal
@@ -634,7 +650,7 @@ async function runOpenCode(params: RunParams): Promise<AgentResult> {
         });
       }
 
-      thinkingTimer.markToolCall();
+      timerFor(label).markToolCall();
       const inputFormatted = formatJsonValue(event.part?.state?.input || {});
       const toolCallLine =
         inputFormatted !== "{}" ? `» ${toolName}(${inputFormatted})` : `» ${toolName}()`;
@@ -671,7 +687,7 @@ async function runOpenCode(params: RunParams): Promise<AgentResult> {
       const output = event.part?.state?.output || event.output;
       const label = eventLabel(event);
 
-      thinkingTimer.markToolResult();
+      timerFor(label).markToolResult();
 
       // surface subagent completion at info level — opencode otherwise hides
       // per-task timing in debug-only logs, so a parallel multi-lens fan-out