docs(vrs): add source-linked language index

[myobie]

What changed

• Add only docs/vrs/ontology.md as a 158-line, 498-word disambiguation index.
• Link each canonical term to its owning Agent Spec, VRS, or implementation source.
• Separate root/catalog root, control plane/declared supervisor, presence/session state, identity/bus ID, and message/DING.
• Reject seat as canonical st2 language while keeping the cited leakage evidence.

Correction from e690cb1

No definition or behavioral text changed. The correction changes only proof-link targets:

• Agent Spec authority now uses the canonical main document and stable section anchors.
• st2 proof links now use the exact symbols and line ranges on current main.
• The branch includes a normal merge from current main; no history rewrite occurred.

Line and word counts are unchanged: 158 lines and 498 words before and after.

Boundaries

This is a source-linked index, not a second specification. It adds no lifecycle, ordering, format, runtime, catalog, or deployment behavior.

Verification at d6b457145f058c64ecd5f6fea6ee753c0cb47766

• Local Markdown targets and line ranges: PASS
• Canonical Agent Spec section anchors: PASS
• Obsolete 78210568 links absent: PASS
• cargo test --test invariants -- --test-threads=1: PASS (1/1)
• cargo test --doc --workspace: PASS
• cargo doc --workspace --no-deps: PASS with five existing main warnings
• git diff --check: PASS
• Hosted Nix: PASS — run 30636215298 / job 91174363298

Nathan approved the meaning-preserving proof-link correction for merge after exact-head gates pass. No deploy or reconcile is authorized.

[myobie]

@schickling-assistant can we start thin with this and work up?

[myobie]

Merging exact head d6b457145f058c64ecd5f6fea6ee753c0cb47766 under the explicit Nathan/CoS authority. The correction changes proof links only; local documentation/link gates and hosted Nix run 30636215298 are green. This merge does not deploy or reconcile runtime state.