v0.1.25 — description capture

Headline: the org's <description> text is now captured and queryable. Four
metadata types silently dropped their descriptions; now every type that carries
one keeps it, and a new missingDescription filter answers "which reports /
objects / permission sets are undocumented?" — previously an honest gap.

Upgrade note: the description is captured at extraction time, so run
sfi refresh once on 0.1.25 to backfill descriptions into an existing vault.

Added

• Description capture across every metadata type that carries one. The
  org's top-level <description> is now extracted into node.properties.description
  for the four generic metadata types that previously dropped it — Report,
  Dashboard, ReportType, and PermissionSetGroup (extractReport,
  extractDashboard, extractReportType, extractPermissionSetGroup in
  enterprise-metadata.ts now pass extraProperties: ['description']). The
  seven custom extractors (CustomObject, CustomField, PermissionSet,
  Profile, Flow, ValidationRule, RecordType) plus CustomTab and
  CustomApplication already captured it. The description renders as a paragraph
  in the component markdown (unchanged renderer). Verified offline against a real
  ~1,300-object source tree: captured counts match the source's
  files-with-<description> ground truth exactly for every generic type (Report
  221, Dashboard 17, PermissionSetGroup 16, plus CustomField 1315, ValidationRule
  306, PermissionSet 159, RecordType 86, CustomObject 75). Only the genuine
  top-level <description> is captured — nested element-level descriptions (e.g.
  a Flow decision's own <description>) are intentionally excluded, and Profiles
  capture their single real top-level description with no fabrication.
• list_components documentation-coverage filter. New missingDescription
  / hasDescription boolean flags answer "which reports / objects / permission
  sets / validation rules have no description?" — previously an honest gap. Backed
  by a descriptionPresence: 'present' | 'absent' narrow in the graph layer
  (queries.ts) that folds key-absent, JSON-null, and empty-string all into one
  honest "absent" bucket via coalesce(json_extract_string(...,'$.description'),'').
  The narrow is applied to both the page query and the authoritative
  countNodesByType total; the two flags are mutually exclusive (invalid-query
  guard). Honesty caveat, disclosed in the tool description: for a type whose
  source carries no <description> element at all (ListView, CustomPermission,
  MutingPermissionSet, CustomMetadata), missingDescription matches every
  node — the answer means "no description in this metadata type", not "left blank".