feat: v2 invite API + CLI claim flow + CLI friction reducer (wave 2)

Wires the v2 invite protocol end-to-end from a CLI user's perspective.
Broker foundation landed in c1fa3bc; this commit is the glue between
it and the human.

API (packages/api)
- createMyInvite now mints BOTH v1 token (legacy) AND v2 capability.
  Two-phase insert: row first (to get invite.id), then UPDATE with
  signed canonical bytes stored as JSON {canonical, signature} in the
  capabilityV2 column. Broker's claim handler parses the same shape.
- canonicalInviteV2 locked to `v=2|mesh_id|invite_id|expires_at|role|
  owner_pubkey_hex` — byte-identical to apps/broker/src/crypto.ts.
- brokerHttpBase() helper rewrites wss://host/ws → https://host for
  server-to-server calls.
- POST /api/public/invites/:code/claim — thin proxy to broker;
  passes status + body through, 502 broker_unreachable on fetch fail,
  cache-control: no-store.
- POST /api/my/meshes/:id/invites/email — mints a normal v2 invite
  via createMyInvite, records a pending_invite row, calls stubbed
  sendEmailInvite (logs TODO for Postmark wiring in a later PR).
- New schemas: claimInviteInput/ResponseSchema,
  createEmailInviteInput/ResponseSchema, v2 fields on
  createMyInviteResponseSchema.
- v1 paths untouched — legacy /join/[token] and /api/public/invite/:token
  continue to work throughout v0.1.x.

CLI (apps/cli)
- New `claudemesh join <code-or-url>` subcommand.
- Accepts bare code (abc12345), short URL (claudemesh.com/i/abc12345),
  or legacy ic://join/<token>. Detects v2 vs v1 and dispatches.
- v2 path: generates fresh ephemeral x25519 keypair (separate from
  the ed25519 identity) → POST /api/public/invites/:code/claim →
  unseals sealed_root_key via crypto_box_seal_open → persists mesh
  with inviteVersion: 2 and base64url rootKey to local config.
- Signature verification skipped with TODO — v0.1.x trusts broker;
  seal-open is already authenticated.
- apps/cli/src/lib/invite-v2.ts: generateX25519Keypair, claimInviteV2,
  parseV2InviteInput.
- state/config.ts: additive rootKey?/inviteVersion? fields.

CLI friction reducer
- apps/cli/src/index.ts: flag-first invocations
  (`claudemesh --resume xxx`, `claudemesh -c`, `claudemesh -- --model
  opus`) now route through `launch` automatically. Bare `claudemesh`
  still shows welcome; known subcommands dispatch normally.
- Removes one word of cognitive load: users never type `launch`.

No schema changes. No new deps. v1 fully backward compatible.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/cli/src/state/config.ts

@@ -26,6 +26,15 @@ export interface JoinedMesh {
   secretKey: string; // ed25519 hex (64 bytes = 128 chars)
   brokerUrl: string;
   joinedAt: string;
+  /**
+   * Mesh root key (32 bytes) as URL-safe base64url, no padding.
+   * Present for v2 invite joins (sealed then unsealed client-side).
+   * Absent for v1 joins, where the root key lives inside the saved
+   * invite token on disk instead. Used by channel/group `crypto_secretbox`.
+   */
+  rootKey?: string;
+  /** Invite protocol version used to join. `2` for v2, omitted/`1` for legacy. */
+  inviteVersion?: 1 | 2;
 }
 
 export interface GroupEntry {