Add 11 diagrams, vendor mermaid, and stop the site fetching code from a CDN

[rocklambros]

Adds 11 diagrams to the specification and concept documentation, and fixes two problems found while verifying they actually display.

The diagrams

Eleven across nine pages, placed where a reader meets each mechanism rather than collected in a gallery. The runtime path and the constraint that the LLM layer cannot read policy code, the handshake, the five dispositions, the hook taxonomy, the session lifecycle, the Trace mappings into OpenTelemetry and OCSF, the AgBOM serializations, conformance profile layering, and the in-action walkthrough.

Before this, docs/acs.md at 773 lines, specification.md at 433, and ACS_in_action_example.md at 263 carried a wire protocol, a two-layer Guardian, five dispositions, and a full scenario in prose alone.

Two problems found by rendering them in a browser

The published site fetches executable JavaScript from a third party. mkdocs-material's bundle lazily loads mermaid from https://unpkg.com/mermaid@11/dist/mermaid.min.js whenever it meets a diagram. Verified live: loading the current published identity/standards page issues that request. The version is a range, so unpkg decides which 11.x a reader executes.

The third-party guard missed it because stray_scripts allowlists the theme bundle by digest and never reads what is inside it. Confirmed three ways: third_party_hosts on the rendered page returns none, stray_scripts returns none, and the allowlisted bundle contains two unpkg URLs.

Mermaid has never rendered on this site. The one diagram already in docs/identity/standards.md resolves to an empty element with no SVG on the live site today. The theme's pass replaces the source block with an empty div before drawing, so the text is gone by the time mermaid is asked for a picture.

The fix

Mermaid 11.17.2 is vendored at docs/assets/javascripts/mermaid.min.js and declared through extra_javascript. The superfences custom fence now emits class acs-diagram rather than mermaid, so the theme does not recognise a diagram, never reaches its loader, and never empties a block. mermaid-init.js renders from the vendored copy. Authors still write ```mermaid fences and GitHub still renders them natively.

Cost: 3.5 MB uncompressed, about 956 KB gzipped, on pages that load it.

Guards

stray_scripts now accepts a built script whose digest matches a file in docs/assets/javascripts/, which proves it is byte-identical to what is committed here rather than merely allowed by path.

A new guard asserts that package-CDN references in built JavaScript match a reviewed set. The three surviving unpkg references are documented with why each cannot fire. Proven by injection: adding a jsdelivr URL fails the test, removing it passes.

NOTICE records the MIT attribution, matching the standard the file already sets for the Inter font and the AGT bundle.

Verification

Every diagram rendered in a real browser, not asserted from a bracket count. 11 of 11 produce SVGs across all nine pages, zero raw blocks remain, and zero third-party requests are issued. 206 tests pass, mkdocs build --strict clean.

The merge-base changed after approval.