feat(revit): keynote assignment sync — element keynote params via parameter mappings

[thewrz]

Context

ADR-016 D4. The add-in assigns keynote values to model elements; assignments persist through the revit_parameter_mappings pattern so element↔keynote↔spec joins surface in the link inventory rather than a new subsystem.

Scope

Create:

• Add-in reads/writes element keynote parameters
• Assignments persisted via the revit_parameter_mappings pattern

Acceptance

• Assignment round-trip: set in model → visible via the link inventory read model (feat(api): revit link inventory — element↔spec mapping read model #103)
• Keynote pointing outside project TOC flagged in the coordination report (feat(api): project coordination report — missing sections, broken refs, unmapped elements #105)

Blocked by

#48, #99

Out of scope

Keynote legends, drawing-side artifacts.