Resolve Markdown item references with authorization #86

Work

Integrate the canonical resolver from #73 into the Markdown syntax tree. Resolve bare #N in the owning project and documented qualified references elsewhere. Skip fenced/inline code, escaped references, existing links and URL fragments. Deduplicate/batch resolution for performance.

Acceptance

• References to task and memory items navigate correctly.
• Missing, inaccessible and ambiguous legacy references render neutrally without revealing metadata.
• No nested anchors or accidental references in code.
• Expose extracted canonical targets to #75 for backlinks; parsing alone does not mutate published graph state.

Dependencies

#73 resolver and #74 renderer; backlink persistence belongs to #75.