- Simplify JavaScript column field context:
- expose `isPk` instead of `isPrimaryKey`
- expose `defaultExpression` instead of separate SQLite default flags
- remove value/default state from plugin context
- Update field helper behavior:
- `setValue()` no longer dispatches input/change events
- remove dispatch options and `resetValue()`
- add `markClean()` for plugin-normalized initial values
- track clean field state for reliable dirty detection
Also:
- Prompt before closing row insert/edit dialogs when there are unsaved changes
- Map declared SQLite types to affinities, returning `BLOB` for typeless columns and `NUMERIC` for numeric/date/boolean-like declarations
Replace the value/valueType/originalValue/originalValueType fields on makeColumnField() contexts with an explicit field object API for reading, writing, resetting, comparing and validating field values.
Normalize columnType to {type, config}, rename the SQLite default metadata so it is clearly SQLite-specific, and document that plugins submit only string, number, boolean or null values. Plugins that need structured data should serialize it themselves instead of relying on Datasette to special-case JSON.
Move the built-in json column type behavior onto the same plugin API used by external plugins: validate the textarea with field.setValidity() as the value changes, but submit plain text. Harden row edit value comparison so fixing invalid JSON in an existing row is not blocked by the original invalid value.
Update the JavaScript plugin documentation and Node-based tests for the revised field contract.
