Adds two enum-style column types where the column declares a fixed set of
options (stable id + name + palette color) and every cell is constrained to
them.

- COLUMN_TYPES gains `select` / `multiselect`; SELECT_COLORS is a fixed,
  theme-aware palette mapping 1:1 to Badge color variants (no raw hex)
- ColumnDefinition.options carries the option set. Cells store option *ids*
  (a string for select, string[] for multiselect) so renaming or recoloring
  an option never rewrites row data
- Row validation enforces membership; coercion tolerantly maps an option
  *name* to its id for tool/import writes and drops unmatched entries
- validateColumnDefinition enforces non-empty, unique-id, unique-name and
  valid-color option sets, and rejects options on non-select columns
- Contract gains selectOptionSchema plus a cross-field refine requiring
  options exactly on select types; routes thread options through type
  changes and a new options-only updateColumnOptions path

No migration: column config already lives in the user_table_definitions
schema JSONB blob.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014e4MvFV1szLhNLap1CCNUd

Addresses review findings on the select/multiselect column types:

- Column type conversion now checks each existing value against the target
  option set (resolve by id or name); a `select`/`multiselect` change is
  blocked when values don't fit, instead of accepting shapes that later
  coercion would strand or silently drop
- Inline select editor discards its draft on Escape (matching the text/date
  editors) rather than committing on menu close
- A required single-select no longer offers "None" — clearing to null could
  never be committed

Exports resolveSelectOptionId from validation for the conversion gate.

Round 2 review fixes:

- A required multiselect can no longer be emptied — the toggle that would
  remove the last option is ignored, since an empty selection can't be
  committed (server rejects it). Mirrors the required single-select "None"
  guard.
- Inline cell save now compares old vs new value structurally, so a no-op
  edit (e.g. opening a multiselect and closing it unchanged, producing a new
  array reference) no longer writes a row update or pushes an undo entry.
  Uses JSON compare for arrays/objects, matching the existing optionsEqual
  convention; primitives keep the === fast path.

Round 3 review fixes:

- Expanded-cell popover normalizes a multiselect's initial value with
  toSelectedIds, so a single option-id string (the normal shape right after a
  select->multiselect conversion, before the row is rewritten) is no longer
  collapsed to an empty array and cleared on save.
- Column PATCH now only routes to updateColumnType on a real type change.
  updateColumnType early-returns on an unchanged type, so a payload repeating
  the current type together with new options previously applied neither; an
  unchanged type with options now routes to the options-only update. Fixed in
  both the internal and v1 column routes.

- Double-clicking a select/multiselect cell now opens the inline option
  dropdown (like date/number) instead of the fixed-height text popover, which
  rendered just a small dropdown floating in a large empty container. Removes
  the now-unreachable ExpandedSelectEditor from the expanded-cell popover.
- Options editor's add/remove controls match the sibling Filter UI: a ghost,
  muted "Add option" button with a small plus, and an X remove icon.

Two spots where the check and the migration disagreed, each leaving a cell the
check had already accounted for:

- resolveSelectOptionId matches option names case-insensitively, so a cell like
  'open' against option 'Open' passed the convert-to-select check, but the
  migration map was case-sensitive and left it as the raw name. The map now
  keys the folded name too (duplicate names are already rejected
  case-insensitively, so it is unambiguous) and lookups try the exact form
  first.
- Converting away from select, the check treats an orphaned option id as null
  while the migration passed it through, so a column with deleted-option cells
  could land an opaque opt_ id in a number/date/boolean cell. Orphans now null,
  matching selectValueForConversion; a multi cell drops them and nulls when
  nothing survives.

This reverses the pass-through choice from the earlier round — consistency with
the check is what matters, and an orphan is a value the UI never rendered.

`[]` is the canonical empty multiselect but it is not falsy, so every
emptiness check that only looked for null/undefined/'' read a cleared selection
as filled:

- dependent workflow groups became eligible off an empty cell, and enrichments
  with a required input ran on rows they should have skipped
- marking a column required did not count `[]` rows, even though write-path
  validation rejects an empty required multiselect

One `isEmptyCellValue` predicate now backs the dep, output-filled and
enrichment checks, and the required-constraint guard counts '[]' too.

Also normalizes '' on conversion to select — compatibility admits it, so it has
to land as null (single) or [] (multi) rather than a bare string the column's
own validation would then reject.

updateColumnType early-returns when the type is unchanged, so an agent that
restated newType: 'select' alongside a new option set had those options
silently dropped while the tool still reported success. The HTTP columns route
already guards this; the copilot path now mirrors it — only a genuine type
change goes to updateColumnType, anything else with options or multiple goes to
updateColumnOptions.

A payload that only restates the current type is a no-op and now reports the
live schema rather than an undefined one.

…ion errors to 400

- The delete-column undo snapshot never captured options or multiple, so
  re-creating a select column was rejected outright (it is invalid with no
  option set) and the saved cell data — which is option ids — had nothing to
  attach to. Undo of a select column deletion simply could not succeed.
- The v1 add-column route mapped only 'already exists' and 'maximum column' to
  400, while the internal route also maps invalid-column and option errors. A
  bad select option set surfaced as a 500 on the public API.

…select

The clearing lived only in the column-config sidebar, so a conversion through
the v1 API or the copilot tool left unique: true stranded on a select column —
where the constraint compares the stored option id, capping each option at one
row for the whole table, and the sidebar hides the toggle so it could never be
cleared again.

Moving it into updateColumnType gives all three callers the same behavior; the
sidebar's payload is now belt-and-braces rather than the only enforcement.