[jm-rivera]

Stacks on #43.

The DataSearch components and the src/lib/search helpers take the page's spec, part and binding types in place of any, so a reader that skips an absent member fails to compile. 112 such parameters are typed. Three remain, each at a boundary: flattenPart in searchClient.ts reads an unvalidated response body, and previewColumns.test.ts edits a trimmed fixture in place.

SpecReading in types.ts is Partial<Spec> | UnreadableSpec, the shape a helper that accepts any part's spec reads, and UnreadableSpec.stat_vars is unknown, the raw value that failed validation. A spec's StatVars reach a reader only through readStatVars in view.ts, which returns nothing for an unreadable spec. Nested members keep the wire's optionality, which exposed readers that assumed a bare coverage has dimensions, that requested_window is never 'latest', and that entity_type and download are never null. Test fixtures go through partialSpec and partialSlot in test/fixtures/partial.ts, which take a deep partial of the wire type, so each member a fixture names keeps its wire name and type. Two fixtures named members ObservationSeries lacks (series_key and index) and now name stat_var.

Three behaviours change, and a reviewer should confirm each. A spec flagged statVarsUnreadable supplies no StatVar count, years or members read from the value that failed validation, so the measure token's About drops its count and span and the Why panel counts no variables (servedMembership, servedSeriesCount, yearsText and buildWhySummary in view.ts, and servedSpan, latestDate and singleStatVarSpec in tokenAbout.ts). priceBasis in unitLabel.ts reads a prices value other than current or constant as unknown and falls back to the unit ref and the qualifier, where it printed the unknown value as constant prices. withResolvedSlotEdit in promote.ts returns the identity unchanged for a spec with no slots, where it threw, a path no rendered slot menu reaches.

Testing: typecheck, lint, lint:css, the 1,613 tests outside db/ and pnpm build pass. A new why.test.ts case gives an unreadable spec with { served_count: 3, member_count: "3" } to the measure About and buildWhySummary, and fails when readStatVars is bypassed.