fix: preserve compaction provenance through resume and harden memory retrieval

Carry allowlisted summary origin and host user ledger across the trace recovery boundary. Keep immutable snapshot links after alias failures, scope legacy padded keys, remove stale indexes under small budgets, reuse retrieval clues for labels, and add cross-platform memory CI.

.github/workflows/context-memory.yml

@@ -0,0 +1,23 @@
+name: Context memory
+on:
+  push:
+    paths: ['internal/agent/**', 'internal/app/**', 'internal/config/**', 'internal/database/**', 'internal/handler/**', 'internal/mcp/**', 'internal/multiagent/**', 'internal/project/**', 'internal/projectprompt/**', 'go.mod', 'go.sum', '.github/workflows/context-memory.yml']
+  pull_request:
+    paths: ['internal/agent/**', 'internal/app/**', 'internal/config/**', 'internal/database/**', 'internal/handler/**', 'internal/mcp/**', 'internal/multiagent/**', 'internal/project/**', 'internal/projectprompt/**', 'go.mod', 'go.sum', '.github/workflows/context-memory.yml']
+permissions:
+  contents: read
+jobs:
+  memory:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - run: git config --global core.autocrlf false
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - name: Test compaction, resume, snapshots and scoped memory
+        run: go test -race ./internal/agent ./internal/app ./internal/database ./internal/handler ./internal/multiagent ./internal/project ./internal/projectprompt