feat(cli,broker): stable session identity — fix ghost peers + lost DMs (1.35.0)

Session identity is now anchored on Claude Code's session UUID instead of a
fresh random keypair per launch. The ed25519 session keypair is generated
once per (mesh, session UUID) and persisted under
~/.claudemesh/sessions/<mesh>/<uuid>.json, so relaunching or --resume-ing the
same session reuses the same sessionPubkey.

Why: a DM is sealed (crypto_box) to the recipient's sessionPubkey. With
ephemeral per-launch keys, the pubkey rotated on every relaunch, so queued
messages became undecryptable AND the old presence lingered as a same-name
ghost that won queued-DM claim races. Reconnecting could not recover the
peer because it minted yet another key. On --resume the CLI also registered
a throwaway random id unrelated to the resumed session, so the broker never
recognized the returning peer.

CLI (launch.ts):
- resolve the stable UUID for all paths: fresh mints + forces via
  --session-id; --resume V registers V; --continue resolves the most-recent
  session UUID from ~/.claude/projects/<cwd>.
- use loadOrCreateSessionKeypair(mesh, uuid) instead of generateKeypair().

CLI (daemon/run.ts):
- onRegister closes any prior SessionBrokerClient holding the same pubkey
  under a different token (the leaked-WS ghost).

Broker (handleSessionHello):
- reattach by sessionPubkey regardless of lease state (online or grace),
  closing the stale socket — enforces one live presence per session pubkey,
  killing the duplicate and draining queued DMs on return.

Trade-off: session secret keys now persist on disk (the member key already
does); SPEC.md updated to reflect the stable-identity model. Older CLIs
remain compatible (they keep using ephemeral keys).

New: keypair-store.ts + 7 unit tests. Full CLI suite: 114/114 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

SPEC.md

@@ -28,7 +28,7 @@ A peer is a Claude Code session connected to a mesh. Ephemeral — comes and goe
 Two-layer identity:
 
 - **Member identity** — permanent, created by `claudemesh join`. Keypair stored in `~/.claudemesh/config.json`. Proves authorization to connect.
-- **Session identity** — ephemeral, generated on every `claudemesh launch`. Fresh ed25519 keypair per session. Provides routing and E2E encryption. Two sessions from the same member have distinct session keys — they can message each other.
+- **Session identity** — anchored on Claude Code's session UUID (the same identity `--resume` is built on). An ed25519 keypair is generated once per `(mesh, session UUID)` and persisted under `~/.claudemesh/sessions/<mesh>/<uuid>.json`, so relaunching or resuming the same session reuses the same `sessionPubkey`. Provides routing and E2E encryption. Two distinct sessions from the same member have distinct session keys — they can message each other. Because a DM is sealed to the recipient's `sessionPubkey`, a stable key is what lets queued messages both route to and decrypt on the returning session; the broker enforces one live presence per session pubkey.
 
 ### Peer attributes
 
@@ -39,7 +39,7 @@ Two-layer identity:
 | groups | `--groups` flag, wizard, or `join_group` | No | Routing labels with optional per-group role |
 | status | Hook-driven | No | idle / working / dnd |
 | summary | `set_summary` tool call | No | 1-2 sentence description of current work |
-| sessionPubkey | Generated on connect | No | Ephemeral ed25519 pubkey for routing + crypto |
+| sessionPubkey | Persisted per `(mesh, session UUID)` | Yes (per session UUID) | ed25519 pubkey for routing + crypto; stable across relaunch/`--resume` |
 | memberId | From `claudemesh join` | Yes | Permanent mesh membership identity |
 
 ### Launch