chore(cleanup): R-b R1 — Voyage's own stats, events and OTel export removed

Removes Voyage's measurement, statistics and export apparatus (decision 189;
condition 175 met in step 1) and the R-a leftovers: lib/stats/, lib/exporters/,
the otel-export and post-bash-stats hooks, yardstick, end-state and comparison
gates, synthesis-measure, gold-scorer, docs/observability.md,
examples/observability/, docs/T1-cc26-delegated-orchestration.md and their
tests and fixtures. The six command stats phases and the /trekexecute
main-merge event blocks go; intent-approval --stamp no longer emits
brief-approved. README and docs point to Claude Code's own OpenTelemetry.

Files removed: 52. Files edited: 37.
npm test: 2930 tests (2928 pass / 0 fail / 2 skipped) before, 2600 tests
(2598 pass / 0 fail / 2 skipped) after. removed-surfaces group R1 green.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

hooks/hooks.json

@@ -54,16 +54,6 @@
       }
     ],
     "PostToolUse": [
-      {
-        "matcher": "Bash",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "node",
-            "args": ["${CLAUDE_PLUGIN_ROOT}/hooks/scripts/post-bash-stats.mjs"]
-          }
-        ]
-      },
       {
         "matcher": "Bash|ExitPlanMode",
         "hooks": [
@@ -108,15 +98,6 @@
       }
     ],
     "Stop": [
-      {
-        "hooks": [
-          {
-            "type": "command",
-            "command": "node",
-            "args": ["${CLAUDE_PLUGIN_ROOT}/hooks/scripts/otel-export.mjs"]
-          }
-        ]
-      },
       {
         "hooks": [
           {