docs(memory,flow): cross-ref shared .backup/ namespace + drop stale prax/.backupignore

Completes the backup-docs sweep (td-218):
- @memory README: note rollover writes rollover_backup_*.json to <branch>/.backup/
- @flow README: note closed plans archive to <repo-root>/.backup/processed_plans/
  both cross-referencing @backup's canonical README.
- Removed orphaned src/aipass/prax/.backupignore (prax is not a registered
  backup target; only the AIPass project root is).

seedgo green across all three (@flow 100, @memory 100, @prax 99 = pre-existing
Json_Handler, unrelated).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QEQZXCtgnF3NQtcttTErpq

CHANGELOG.md

@@ -45,6 +45,8 @@ PyPI version — not the changelog header.
   were fixed. Root README lists @backup and documents `.backupignore`; the navmap
   was corrected. The shipped root `/.backupignore` was realigned to
   `BUILTIN_IGNORES` (dropped stale `.backup_system/` + over-broad `*logs`).
+  @memory and @flow READMEs now cross-reference their `.backup/` writes, and the
+  orphaned `prax/.backupignore` (a stale per-branch config) was removed.
 
 ## [2026-06-23]
 

src/aipass/flow/README.md

@@ -146,6 +146,8 @@ On `drone @flow close`:
 
 Vector verification displays in console: "Vectorized: N chunks in chroma" or "NOT vectorized".
 
+Closed plans are archived to `<repo-root>/.backup/processed_plans/`, a shared runtime namespace managed by `@backup` (see `src/aipass/backup/README.md`) and consumed by `@memory` for vectorization.
+
 ---
 
 ## Integration Points

src/aipass/memory/README.md

@@ -87,6 +87,8 @@ detector.check_all_branches()        # scan AIPASS_REGISTRY.json + external regi
   → trim source file                 # write back with oldest removed
 ```
 
+Rollover writes safety copies (`rollover_backup_*.json`) into `<branch>/.backup/` — a shared runtime namespace (see `@backup`'s README for all writers).
+
 ### Subprocess Isolation
 
 All ML operations (fastembed, chromadb) run via subprocess. The main process never imports these libraries. Python interpreter resolved via `_get_memory_python()` (env var `AIPASS_MEMORY_PYTHON` → `memory/.venv/bin/python` → `sys.executable`).

src/aipass/prax/.backupignore

@@ -1,39 +0,0 @@
-# Backup System ignore patterns (gitignore-style)
-# Lines starting with # are comments. Blank lines are ignored.
-
-# Backup system's own directory
-.backup_system/
-
-# Version control
-.git/
-.svn/
-.hg/
-
-# Python
-__pycache__/
-*.pyc
-*.pyo
-*.egg-info/
-.venv/
-venv/
-.tox/
-
-# Node
-node_modules/
-
-# IDE
-.vscode/
-.idea/
-*.swp
-*.swo
-
-# OS
-.DS_Store
-Thumbs.db
-
-# Build artifacts
-build/
-dist/
-
-# Logs
-*.log