fix(newos4): memory-graph loads stop rewriting user data; unknown sizes say unknown

Three follow-ups from the merge review, each with the assertion that pins it.

module-memory-graph.js
- _normalizeEdges no longer mutates stored weights. It capped legacy 'failed' edges
  from 0.8 to 0.2 in memory, and the next debounced save made that permanent - an
  irreversible migration of the user's graph with no schema version. The cap moved to
  _effectiveWeight(), which ranking (showStats "Strongest relationships"), the session
  view and prune() now use; the stored record is left exactly as written.
- config.json is stamped version: 2 so a future format change can migrate deliberately.

ext/webdav.js
- the two fallback parsers emit size: null instead of 0. They cannot see the size
  column, and 0 rendered as "0 B" - the same "every file looks empty" symptom as the
  parseInt bug fixed in e639c2d, one regex miss away.
- _formatSize(null) renders '—' (unknown) rather than '0 B'; 0 still renders '0 B'.

module-aiassist.js
- the lock timeout now says what to do: "AI is still busy with another turn (waited Ns).
  Wait for it to finish, or run 'ai-stop' and retry - the running turn's lock is left
  alone." It used to be a dead-end string.

Tests: test-memory-graph 39 (T6.4 rewritten to the read-time contract: stored weight
stays 0.8, effective 0.2, success unaffected), test-webdav-sizes 28 (A14d null -> '—').
maintain 26/26, live v4.6.141: _effectiveWeight 0.2 with the edge object unchanged,
_formatSize(null) '—', '0 B' still '0 B'.

1 files changed, 9 insertions, 2 deletions

diff --git a/modules/test/test-memory-graph.js b/modules/test/test-memory-graph.js
index d4fe37a..8c3bb6e 100644
--- a/modules/test/test-memory-graph.js
+++ b/modules/test/test-memory-graph.js
@@ -220,8 +220,15 @@ const sessionOf = d => 'session-session-' + Math.floor(new Date(d).getTime() / 8
         mg2._edges.every(e => Array.isArray(e.source_agents) && typeof e.weight === 'number'),
         JSON.stringify(mg2._edges));
     const legFailed = mg2._edges.find(e => e.type === 'failed');
-    ok('T6.4 a legacy 0.8 failure is capped below success on load',
-        !!legFailed && legFailed.weight < 0.5, 'weight ' + (legFailed || {}).weight);
+    // The cap is applied at READ time, not by rewriting the store: a load must not mutate
+    // user data (the next debounced save would have made it permanent, silently).
+    ok('T6.4a a legacy 0.8 failure is NOT rewritten on load',
+        !!legFailed && legFailed.weight === 0.8, 'stored weight ' + (legFailed || {}).weight);
+    ok('T6.4b it ranks at 0.2 through _effectiveWeight',
+        !!legFailed && mg2._effectiveWeight(legFailed) === 0.2, 'effective ' + (legFailed && mg2._effectiveWeight(legFailed)));
+    ok('T6.4c a success edge keeps its own weight',
+        mg2._effectiveWeight({ type: 'used', weight: 0.5 }) === 0.5,
+        String(mg2._effectiveWeight({ type: 'used', weight: 0.5 })));
     ok('T6.5 unrelated legacy weights are untouched',
         (mg2._edges.find(e => e.type === 'executed') || {}).weight === 0.6,
         String((mg2._edges.find(e => e.type === 'executed') || {}).weight));