feat: add memory.patch, trim memory.get, unify the memory write path

memory.get no longer returns the embedding and content_tsv
----------------------------------------------------------
It used a bare select() and returned the raw DB row, while memory.list
and memory.search already projected an explicit 9-field shape. On a
~13k-char memory those two internal columns were 55% of the response
and pushed it past the MCP tool-output cap, so large memories could not
be fetched inline at all. memory.get now returns the same 9 fields as
its siblings; user_id is still selected for the authorization check and
stripped before responding.

memory.patch
------------
memory.update only accepts full replacement, so adding one line to a
large document meant resending the whole document — expensive enough
that edits were being skipped rather than risk silently truncating
shared team documents.

memory.patch replaces one exact occurrence of old_string. An absent or
ambiguous match is an error, never a silent no-op and never an
arbitrary pick; that refusal is what makes the operation safe to hand
to an agent. The semantics live in lib/memory-patch.ts as a pure
function, free of DB and auth, so both surfaces share them.

Shared mutation layer
---------------------
The MCP tools and the Web UI Server Actions each reimplemented
authorize -> mutate -> re-embed -> CAS -> audit, and had drifted. Both
now route through lib/memory-mutations.ts.

BEHAVIOUR CHANGE: memory.delete over MCP skipped the project ACL
whenever the caller authored the row, so a memory written while a share
was rw stayed deletable by its author after an owner downgraded that
share to ro. memory.update and the whole Web UI always checked.
Authoring a row now grants no standing write privilege on any path.

The one deliberate difference between the surfaces is injected as a
ProjectResolver: MCP refuses an unknown project key so an agent cannot
spawn near-miss projects off a typo, while the Web UI creates one
because a person typing a name into a form means to.

Tests and lint
--------------
Adds vitest. The integration tests run against a real Postgres rather
than a mocked DB. The embedder sidecar is the only stub and it is
deterministic per-text, so re-embedding is verified by asserting the
stored vector actually changed rather than that a mock was called. One
test pins that content_tsv is a generated column and therefore cannot
rot after a patch — only the embedding needs an explicit recompute.

pnpm lint previously dropped into an interactive `next lint` setup
prompt and exited 1; ESLint had never been configured here. Replaced
with the ESLint CLI and a flat config bridging eslint-config-next
through FlatCompat. Clean at --max-warnings=0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/web/eslint.config.mjs

@@ -0,0 +1,33 @@
+import { dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+import { FlatCompat } from "@eslint/eslintrc";
+
+/**
+ * ESLint flat config.
+ *
+ * `next lint` is deprecated (removed in Next 16) and was never configured
+ * here, so `pnpm lint` used to drop into an interactive setup prompt and
+ * exit non-zero. This runs the ESLint CLI directly instead.
+ *
+ * `eslint-config-next` is still published in the legacy .eslintrc format,
+ * so FlatCompat bridges it into flat config. That bridge goes away when
+ * the config ships a native flat export.
+ */
+const compat = new FlatCompat({
+  baseDirectory: dirname(fileURLToPath(import.meta.url)),
+});
+
+const config = [
+  {
+    ignores: [
+      ".next/**",
+      "node_modules/**",
+      "next-env.d.ts",
+      // Generated SQL/journal artifacts from drizzle-kit.
+      "drizzle/**",
+    ],
+  },
+  ...compat.extends("next/core-web-vitals", "next/typescript"),
+];
+
+export default config;