docs: align inline-mentions page with concept-model spec

[ronaldtse]

Summary

• Aligns src/content/model/inline-mentions.mdx with the canonical spec at concept-model/docs/design/inline-mentions-implementation-guide.md.
• Aligns src/content/docs/software/glossarist-js.mdx parseMention examples with the same spec.

Why this matters

The inline-mentions page had drifted from the spec in several load-bearing ways:

• Invented urn kind. The page documented {{urn:URN}} as a kind. The spec has no such kind — URN is a target type, used as {{concept:urn:...}} or {{cite:urn:...}}.
• Allowed bare {{designation}} and {{112-01-10}}. Spec rejects these at parse time — every mention must carry a kind prefix.
• Wrong cite semantics. Page framed cite:sourceId as a local lookup in sources[]. Spec says cite:DATASET:ID resolves a concept first, then optionally matches a ConceptSource — no pre-declaration required.
• Made-up 4-step cascade instead of the spec's parse → resolve phases with per-kind target validation.

What changed

src/content/model/inline-mentions.mdx (full rewrite):

• Canonical 8-kind table (concept, cite, fig, table, formula, bib, link, image)
• Per-kind target validation table (which kind accepts which target shape)
• Structured target parsing table (URN, dataset_qualified, entity_id, url, path) with last-colon split rule
• Resolution algorithm per kind (concept lookup, cite source matching, entity lookup, link/image)
• Common-errors table from the spec
• Preserved the still-accurate Data/Deployment Boundary framing and the deprecated <<ref,title>> migration section

src/content/docs/software/glossarist-js.mdx:

• parseMention() (singular) → parseMentions() (plural, returns segments per spec)
• Removed the invalid {{urn:...}} example
• Updated examples to use realistic DATASET:ID and URN forms
• Linked to /model/inline-mentions for the full reference

Test plan

• npm test — 627 tests pass (was 624; content-references test picked up additional patterns from the rewritten page)
• npm run build — 105 pages
• No AI attribution trailers
• Reviewer spot-check: the kind table, target-type table, and resolution sections match the implementation guide §1.1–1.2