Add capsule signing and trust presentation

[robinbraemer]

Outcome

Define and implement signing and trust presentation for .flect capsules without confusing provenance with permission.

Provide:

• a canonical signed-content representation;
• publisher key and signature metadata;
• verification states for unsigned, valid, invalid, changed-after-signing, and locally forked artifacts;
• user-facing provenance and review presentation;
• key rotation and revocation semantics; and
• policy hooks for products or organizations that require approved publishers.

Exclusions

• Automatically granting capabilities to signed capsules.
• Claiming a valid signature makes code safe.
• Requiring one global publisher registry for all Flect installations.

Acceptance criteria

• Valid fixtures verify identically in browser and desktop hosts.
• Any signed-byte change invalidates verification.
• Forking records lineage and produces an explicitly unsigned or newly signed result.
• Invalid, revoked, or unknown signatures receive clear policy outcomes without exposing cryptographic internals as generic runtime failures.
• Permission prompts and grants remain unchanged by signature status unless an explicit organizational policy denies installation.

[robinbraemer]

Product-quality coverage: FQ-09.3, FQ-10.3, FQ-10.7, FQ-22.3, FQ-22.4, FQ-23.2, and FQ-23.5. Provenance remains explicitly separate from authority.

[robinbraemer]

Pushed local-ready evidence — 2026-08-10

Canonical Ed25519 signed content, publisher metadata, key validity/rotation/revocation policy, unsigned/valid/invalid/changed/forked trust states, protected provenance presentation, and permission-independent policy behavior now pass source and production Chromium fixtures.

Evidence is pushed on codex/flect-vision-complete. This issue remains open until integration.