Replace the old Variables page (which just listed programs with GitHub links)
with a full explorer of all ~4K variables from the metadata API. Features:
- Search across name, label, description, module path, entity, and type
- Multi-word search (each word matched independently across all fields)
- Level filter pills: Federal, State, Local, Territories, Contrib, Household
- Grouped browse mode by agency/state/locality when not searching
- Expandable computation tree showing adds/subtracts recursively
- Shared metadata cache between variables and programs pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Replace flat group list with drill-in level cards (Federal, State, etc.)
- Remove entity filter and input/computed filter toggle (keep as label with tooltip)
- Add level filter pills when searching
- Fix adds/subtracts which can be objects from the API, not just arrays

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…trib category

- Replace flat variable list with visual drill-in: level cards → sub-group cards/tiles → variable list
- Add StateTileGrid with 2-letter state codes and intensity-based opacity
- Add SubGroupCardGrid for federal agencies, local, household, territories
- Embed flowchart iframe at bottom that updates when clicking "View in flowchart" on a variable
- Remove contributed/reform categories (deprecated paths)
- Add level filter pills to search mode

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Create ParameterExplorer with same drill-in pattern as variables (level → sub-group → list)
- Show value history timeline, current value badge, unit, and GitHub source link
- Filter to leaf parameters only (exclude nodes and contrib)
- Extract shared categorization logic to shared/categoryUtils.ts
- Refactor VariableExplorer to use shared utils

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Fix branch: master → main across all GitHub URLs
- Fix variable source links to point to .py files (blob) not directories (tree)
- Add 'reform' level for gov.contrib/contrib parameters
- Remove contrib filter from parameter explorer so reform params are visible

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Add scripts/fetch-metadata.js to download US/UK metadata at build time
- Write to public/metadata-{country}.json, served from Vercel CDN
- Update fetchMetadata.ts to try static file first, fall back to live API
- Update build script to run fetch before tsc/vite
- Add parameter group intermediate navigation level
- Turns ~67s API load into ~1-2s CDN load

Requires deploy hooks from policyengine-us and policyengine-uk to trigger
rebuilds when new model versions are released.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…tion

- Direct YAML file links via pre-built param tree (longest-prefix match)
- Build script fetches GitHub repo tree for exact file mapping
- Truncate long parameter paths in cards
- Filter out 3,355 abolition parameters (internal toggles)
- Add behavioral responses description to Simulation sub-group

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…le colors

Replace flat parameter group list with hierarchical folder navigation that
mirrors the actual parameter file structure. Sub-folders auto-collapse when
they have only one child. Remove intensity-based color scaling from state tiles
so all states appear with uniform color.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Scale the iframe to 75% using CSS transform so more of the
computation flowchart is visible within the same viewport area.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Use a proper lookup for entity display names (e.g. tax_unit → Tax Unit,
spm_unit → SPM Unit, benunit → Benefit Unit) in both card badges and
detail metadata.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Rewrite VariableExplorer with folder tree navigation matching parameter explorer
- Add clickable breadcrumb path navigation (GitHub-style)
- Add Google-style numbered pagination for large groups
- Add loading indicator for flowchart iframe
- Remove inaccurate "N variables across M programs" subtitle
- Remove unused VariableList component

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Count parameters at YAML file level instead of per-leaf (67k → 3.6k)
- Handle array/list parameter values with pill tags
- Collapse projected/uprated values (2026+) behind expandable toggle
- Show date ranges in value history (from → until)
- Fix long label overflow with word-break in folder cards
- Filter gov.puf variables from variable explorer
- Fix Vercel config: set framework to Vite with correct output dir

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>