fix(newos4): bound one turn's tool context, honest skill-create, quarantine a corrupt memory graph

The three items the last review and probes left open, each with a test that is red on HEAD.

- MAINT-023 (module-aiassist.js): one agentic turn grew without limit — every role:'tool' body
  was pushed verbatim and only this.context was trimmed BETWEEN turns (measured 6 -> 112 705
  tokens across 8 model calls against maxContextTokens 12 000). Observations are now clipped to
  maxToolResultChars (6 000) with a note saying how much was withheld and to re-read with
  offset/limit, and _boundToolContext() elides the oldest tool bodies once the running total
  passes toolContextBudgetChars (24 000), always keeping the newest 4 verbatim. The ceiling is
  turn-independent: the same ~26 k chars at 8 turns and at 20.
- MAINT-024 (modules/ext/skill-pack-core.js): the command printed "✅ Skill created" with
  fs.writeFile()'s boolean discarded (probe: fresh VFS, success printed, no file), stripped
  invalid characters instead of rejecting the name (My-Skill -> y-kill, DevOps_Thing ->
  evpshing), and treated an unreadable /path argument as the skill body. Now: kebab-case is
  validated (uppercase normalises and the final name is reported; anything else is refused),
  /skills is created on first use, the write and index results are checked, and an unreadable
  body path is an error.
- MAINT-003 (module-memory-graph.js): a corrupt store looked exactly like a fresh install —
  fsReadJSON returns null on a parse failure, so 85 nodes could vanish with no warning and no
  copy. The probe confirmed the loss: seed 6 nodes, truncate nodes.json and export.json, reload
  -> 1 node, no message, nothing in .trash. _quarantineCorrupt() now keeps the unreadable file
  as <name>.corrupt, warns, and then loads from whatever remains.

Tests: test-tool-context-bound.js (11), test-skill-create.js (16), test-memory-graph-recovery.js
(8). RED on HEAD: tool-context crashes on _clipToolResult (exit 1), skill-create 16 assertions
fail on the missing file/index, memory-graph B1/B2/C1 fail (no warning, no .corrupt copy).
Suite now 13/13 files green; maintain --fix reports "node tests 13/13 pass".
Live on v4.6.107: skill-create My-Skill -> ✅ "my-skill"; DevOps_Thing -> Invalid skill name;
/does/not/exist.md -> Cannot read skill body; only my-skill in the index.

1 files changed, 25 insertions, 0 deletions

diff --git a/modules/core/module-memory-graph.js b/modules/core/module-memory-graph.js
index 1cb0919..e802387 100644
--- a/modules/core/module-memory-graph.js
+++ b/modules/core/module-memory-graph.js
@@ -594,6 +594,12 @@ class MemoryGraphModule {
         try {
             const fs = this.terminal.fs;
             if (!fs) return;
+            // MAINT-003: a corrupt store used to look exactly like a fresh one — fsReadJSON
+            // returns null on a parse failure, so the graph started empty with no warning and no
+            // copy of what was there. Quarantine anything unreadable first, then load what's left.
+            this._quarantineCorrupt('export.json');
+            this._quarantineCorrupt('nodes.json');
+            this._quarantineCorrupt('edges.json');
 
             // Try loading from export first
             const exportData = fs.fsReadJSON(`${this._indexPath}export.json`);
@@ -646,6 +652,25 @@ class MemoryGraphModule {
         }
     }
 
+    // MAINT-003: keep an unreadable store aside instead of starting fresh over it.
+    _quarantineCorrupt(name) {
+        try {
+            const fs = this.terminal.fs;
+            const p = `${this._indexPath}${name}`;
+            const raw = fs.readFile(p);
+            if (typeof raw !== 'string' || !raw.length) return false;
+            try { JSON.parse(raw); return false; } catch (e) {
+                const kept = p + '.corrupt';
+                fs.writeFile(kept, raw);
+                this.terminal.print(`⚠️ Memory graph store ${name} is unreadable — kept a copy at ${kept} and starting from what remains`, 'warning');
+                if (typeof fs.deleteFile === 'function') fs.deleteFile(p);
+                return true;
+            }
+        } catch (e) {
+            return false;
+        }
+    }
+
     _saveNow() {
         try {
             const fs = this.terminal.fs;