Docs: binary resolution, cancellation, progress cap, phase-1 deviations

- runbook: how executor binaries are resolved (bins or PATH) and what that
  assumes on oregon (no codex installed) and win10; cancellation and
  max_progress_rounds in the item lifecycle; secrets scrubbed from children.
- design: blocked-by ordering is a TODO (not read by the scheduler); failure
  classification, success-when-tagged, one-time immediate rebuild, retries
  outside the thread-round budget, ID-based new-comment filter.
- executor contract: how core reads ExecResult, kill used for cancel, Windows
  quoting assumptions, codex exec resume without -C/-s.

agentd/store.py

@@ -3,7 +3,7 @@
 state/agentd-state.json:
   {"projects": {PROJECT: {"issues": {issue_uuid: rec}}}, "paused_groups": {group: {...}}}
 rec: seq, runs, thread_id, thread_on [terminal, executor], thread_rounds, tags [...], last_message,
-     seen_comments [...], last_comment_at, retries, retry {at, reason}, rebuild, inflight {...}"""
+     seen_comments [...], last_comment_at, retries, retry {at, reason}, rebuild, progress_streak, inflight {...}"""
 import contextlib
 import fcntl
 import json