M3b plan: task 08 says not to join handler threads and to skip argv[0]

The first attempt at task 08 did both and stopped without a commit. Also asks
the implementer to debug inside the repository, since OpenCode refuses /tmp.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/plans/M3b/README.md

@@ -60,6 +60,11 @@ At the end: `make gate` prints `gate: ok` with about 638 tests.
   its `git add` line left the lock out, so the driver stopped on an unclean tree. The design model
   folded the lock into task 04's commit and added `Cargo.lock` to every task's `git add` (a no-op
   when it has not changed). The owner resumes from task 05.
+- 2026-09-23, task 08: the first attempt passed 13 of 15 tests and ended without a commit, after
+  OpenCode refused a command in `/tmp`. Its two defects: `main` did not skip the program name, so
+  `egress-proxy` never matched; and `serve` joined each handler thread, serving one connection at a
+  time. The attempt is saved in `.state/runs/M3b/08-first-attempt.diff`; the tree was reset, and the
+  task now says both things explicitly and to debug inside the repository. Resume from task 08.
 
 ## Running it