docs: mainnet cutover complete - both hosted instances run the keyless build (deployed 2026-07-31)

David dispatched the mainnet cutover this morning: deploy-mainnet.yml ran successfully at
2026-07-31T11:00:06Z-11:01:20Z, deploying commit 04e410b (the PR #11 merge, itself the tip of
main after PRs #9/#10/#11 all merged 10:39:29Z-10:39:59Z the same morning). Testnet had already
auto-deployed the identical commit at 10:40:01Z-10:41:50Z. The non-custodial migration is now
complete on both hosted instances, not just in the code - the exact moment the prior docs pass's
deliberately-hedged notice was written for.

Verified directly before writing anything, not taken on faith from the dispatch: git/gh confirm
the merge timestamps and that both deploy workflow runs targeted 04e410b exactly; the custody
grep and safety.ts's absence were reconfirmed on this exact commit; both hosted endpoints
(https://mcp.vector.mainnet.apexfusion.org/sse and the testnet equivalent) were probed directly
with a bare curl request and both returned HTTP 401 right now - meaningful evidence on its own,
since the pre-PR#8 image had no auth at all, so a 401 today proves post-migration code is what's
actually running, not just what the deploy logs claim.

- README.md: the deployment-status callout rewritten with the dated, both-networks-current
  facts, replacing the custody caveat with an access caveat - both instances require a bearer
  token from the operators now (an access control, not a custody signal; neither instance would
  accept a mnemonic from an authenticated caller either, since the tool schemas that would carry
  one no longer exist). The connect command now shows the bearer-token header syntax, verified
  against Claude Code's own current `claude mcp add` documentation before writing it (`--transport
  sse` accepts `--header "Authorization: Bearer <token>"`, same as `--transport http`). The
  security notice rescoped from "this codebase, not every deployment" to a dated claim: complete
  in this codebase and on both hosted instances as of the 2026-07-31 cutover deploy specifically,
  explicitly not a "forever" claim - a future deploy is a separate operational action.
- packages/signer/README.md: the two passages scoped to "this codebase" in the prior docs pass
  now scoped to "any instance running the 2026-07-31 deploy or later," mainnet included, with the
  same access-control caveat about the bearer token.
- docs/architecture/non-custodial-split.md: PR-sequence row 9 (mainnet cutover) gets the same
  landed-marker style as rows 6-8, dated; section 11's rollout paragraph gets its one now-historical
  clause corrected to past tense with a dated annotation appended, following the established
  forward-only annotation convention rather than rewriting the paragraph.

Open public access (no token, per-IP rate limiting) remains a planned follow-up, not yet an open
PR or branch - checked directly (gh pr list, git branch -a) rather than assumed, and stated in
the docs as planned, not implied as already in progress.

packages/signer/README.md

@@ -165,10 +165,11 @@ over-counts, which refuses too much rather than too little.
   and the smoke tests above). **Nothing is left open in the code: this was the last custodial
   family.** The non-custodial migration described in
   [`docs/architecture/non-custodial-split.md`](../../docs/architecture/non-custodial-split.md)
-  is complete in this codebase. It is not yet complete on every deployment: the mainnet hosted
-  instance stays on its last custodial image until a deliberate cutover deploy ships (see that
-  document's rollout section). Until then, pair this signer with a self-hosted or testnet
-  builder if you want the guarantee above to actually hold - not the mainnet one.
+  is complete in this codebase, and as of the 2026-07-31 cutover deploy, on both hosted
+  instances too: pair this signer with a self-hosted builder, the testnet instance, or the
+  mainnet instance now, since any of them running the 2026-07-31 deploy or later carries the
+  guarantee above. Both hosted instances currently require a bearer token from the operators
+  to connect - that is an access control, separate from the custody guarantee above.
 
 ## Running it
 
@@ -195,11 +196,10 @@ example):
 ```
 
 Register it alongside the builder so an agent has both sets of tools available. This pairing
-keeps your mnemonic off any server running this release, for every family it exposes: wallet,
-transaction, smart-contract, agent-registry, and self-improvement alike - as long as that
-server is actually running this release. The mainnet hosted instance is not, yet: see the
-deployment status note in the root README before assuming this covers it. See the last bullet
-under Known limitations above for the full evidence.
+keeps your mnemonic off any server running the 2026-07-31 deploy or later, for every family it
+exposes: wallet, transaction, smart-contract, agent-registry, and self-improvement alike. Both
+hosted instances qualify now, and so does any self-hosted deployment of this release. See the
+last bullet under Known limitations above for the full evidence.
 
 ## Testing