refactor(session): fold the session family into packages/session/

git mv the 12 packages from session-persistence/, session-projection/,
session-title/, and telemetry/ into one session/ group per the
regrouping RFC; merge the four group READMEs into one bilingual
triplet; rewrite the group segment in tsconfig references (intra-group
references shorten to ../<pkg>), tsconfig.base.json paths/globs,
knip.json keys, vitest include, gate scripts, and authored doc/note
citations; regenerate module graph, doc graphs, catalogs, and the
lockfile importer keys. No npm names change.

Full unit suite: 8779 passed; the 18 reported failures reproduce as
env flakes (ambient-proxy IPv6 tunneling, watched-dir inotify
timeouts under parallel load) — each passes in isolation with
NO_PROXY set, matching their known pre-existing behavior on master.

packages/session/session-title/tests/invariant.spec.ts

@@ -0,0 +1,44 @@
+// Title-provenance invariant: messageSeqs is empty iff source.kind is 'user'
+// — the durable relationship every appended session/title event must keep.
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import * as SessionTitleInvariantCompanion from '@deepseek-ai/dsh-session-title/invariant'
+import InvariantService, { InvariantError } from '@deepseek-ai/dsh-invariants'
+import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
+
+async function setup(): Promise<Context> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(InvariantService, { enabled: true })
+  await ctx.plugin(SessionTitleInvariantCompanion)
+  return ctx
+}
+
+describe('session-title provenance invariant', () => {
+  it('accepts cited automatic titles and citation-free user renames', async () => {
+    const ctx = await setup()
+    const session = ctx.sessions.create(SessionId('title-invariant-valid'))
+    expect(() => {
+      session.append('session/title', { title: 'auto', messageSeqs: [1], source: { kind: 'fallback' } })
+      session.append('session/title', { title: 'named', messageSeqs: [], source: { kind: 'user' } })
+    }).not.toThrow()
+  })
+
+  it('rejects a citation-free automatic title and a user rename that cites messages', async () => {
+    const ctx = await setup()
+    const session = ctx.sessions.create(SessionId('title-invariant-invalid'))
+    expect(() => {
+      session.append('session/title', { title: 'auto', messageSeqs: [], source: { kind: 'fallback' } })
+    }).toThrow(expect.objectContaining<Partial<InvariantError>>({
+      code: 'INVARIANT',
+      packageName: '@deepseek-ai/dsh-session-title',
+    }))
+    expect(() => {
+      session.append('session/title', { title: 'named', messageSeqs: [1], source: { kind: 'user' } })
+    }).toThrow(expect.objectContaining<Partial<InvariantError>>({
+      code: 'INVARIANT',
+      packageName: '@deepseek-ai/dsh-session-title',
+    }))
+    expect(session.seq).toBe(0)
+  })
+})