Search UX v2 #1: chip infrastructure

[hoyla]

Lays the groundwork for the search UX improvements epic #633.

Closes #634. Incidentally fixes #477, not that that matters much since we move chips out of the search bar in a subsequent branch.

Important

This is the first of five PRs in the Search UX Improvements epic. All other PRs depend on this one — it must be merged first.

PR1 Chip parsing infrastructure  ← you are here
 └─ PR2 Shared utilities & Downshift dependency
     └─ PR3 Active filter chips & multi-select
         └─ PR4 Search page & AddFilterModal
             └─ PR5 Sidebar tri-state filters

Changes to the user experience

This PR is primarily infrastructure, but it does include a few visible changes:

Search bar chip improvements

• Long chip values are truncated — chip values longer than 75 characters are shortened to 72 characters with ..., and hovering shows the full value in a tooltip. This prevents the search bar from being stretched by very long folder paths or search terms.
• Chip name labels are truncated — chip name labels (e.g. "Workspace Folder") are capped at 150px with ellipsis overflow, preventing excessively wide chips.
• Search bar overflow handling — the inline input now respects max-width: 100% with text overflow ellipsis, and the last chip element always reserves at least 100px for typing.

Before:

After:

Having truncation rules will be useful even when we move chips out of the searchbox.

New search chip types

• Language chip — a new "Language" dropdown chip is available in the search bar, allowing users to filter by document language (Arabic, English, French, German, Persian, Portuguese, Russian, Spanish). Selecting multiple languages works correctly with the multi-word template expansion fix.
• Transcription option for Has Field — the existing "Has Field" dropdown chip now includes a "Transcription" option alongside OCR, Text, and Author.

Backend: exclude filters

• The search API now accepts workspace_exclude[] and ingestion_exclude[] query parameters, allowing results from specific workspaces or datasets to be excluded. This is plumbing for the tri-state sidebar filters in PR5 — there is no UI to trigger these yet.

Bug fix

• InputSupper focus crash — fixed a pre-existing bug where pressing the search keyboard shortcut before the search box was fully initialised would crash with Cannot read properties of undefined (reading 'focus').

Notable non-change

• The "Search workspace" and "Search in folder" buttons continue to work exactly as before — navigating to the search page with the workspace ticked in the sidebar. The way this is achieved will change in a subsequent PR to make it more consistent with chip-based query params.

What's included

• Chip parsing and serialisation (chipParsing.ts) — parses q strings into typed chips and rebuilds them. Three chip kinds are supported via a discriminated union: SingleChip, MultiChip, and DateRangeChip.
• Shared chip constants (chipNames.ts) — all magic strings for chip names, types, and kinds live here so typos cause import errors rather than silent runtime bugs.
• File type category mapping (fileTypeCategories.ts) — maps MIME types to user-friendly categories (PDF, Images, Spreadsheets, etc.) for the File Type filter in subsequent PRs.
• Backend query construction helpers — buildWorkspaceSearchQ and buildWorkspaceFolderSearchQ centralise the construction of search queries for workspace navigation, replacing scattered inline logic.
• isRawChip type guard — replaces repeated inline type assertions with a single reusable guard for narrowing raw parsed chips.
• Workspace search button updates — workspace search buttons now use chip-based query parameters rather than manually constructed strings.
• SCSS improvements — shared SCSS variables for chip styling and improved truncation behaviour in the InputSupper component.

TypeScript

All new code is written in TypeScript. Existing chip-related JS files have been converted to .ts/.tsx with full type annotations and discriminated union types for compile-time safety.

Automated tests

Chip parsing logic is covered by unit tests in chipParsing.spec.ts. File type category mapping is covered in fileTypeCategories.spec.ts. Backend chip expansion is covered in ChipsTest.scala.

Manual tests

• Tested locally.
• Tested on playground.