docs: fix 4 stale refs (4-thread->8, dispatch line 1341->1322, 7->11 locks)

Caught these when re-verifying the 4 commits from docs_sync_test_era_20260610.
Not in my track originally (per the prior 'no track boundary' correction),
but they're stale data and easy to fix in one commit:

- docs/Readme.md:41: '4-thread ... 7 lock-protected regions' -> '8-thread
  io_pool ... 11 lock-protected regions' (bumped 4->8 in 4a338486
  on 2026-06-06; 11 locks counted in __init__ at app_controller.py:778-1212)

- docs/reports/session_synthesis_20260608.md:121: same fix, plus a
  note that this report predates the bump

- docs/reports/workflow_markdown_audit_20260608.md:40: same fix
  (the audit report was correct AT TIME OF WRITE but is now stale)

- docs/guide_tools.md:57: 'mcp_client.py:1341' -> 'mcp_client.py:1322'
  (the dispatch function's actual line)

Left unchanged:
- docs/reports/COMPACTION_DIGEST_20260607.md:45 mentions '4 workers are
  stuck' in a specific historical context (2026-06-07 hang investigation
  pre-bump). That '4' was true at the time and is part of the historical
  record; flagging in commit message not text.

docs/guide_tools.md

@@ -54,7 +54,7 @@ The error message includes the full list of allowed base directories for debuggi
 
 ## Native Tool Inventory
 
-The `dispatch` function (`mcp_client.py:1341`) is a flat if/elif chain mapping 45 tool names to implementations. All tools are categorized below with their parameters and behavior. The count grew from the original 26 as Python structural tools (Phase 6) and C/C++ AST tools (Phase 6.5) were added; Beads tools (4) were added for the Beads mode integration.
+The `dispatch` function (`mcp_client.py:1322`) is a flat if/elif chain mapping 45 tool names to implementations. All tools are categorized below with their parameters and behavior. The count grew from the original 26 as Python structural tools (Phase 6) and C/C++ AST tools (Phase 6.5) were added; Beads tools (4) were added for the Beads mode integration.
 
 ### File I/O Tools