JSON column viewer with syntax highlighting

Description

Adds a way to inspect JSON columns as pretty-printed, syntax-highlighted documents instead of squeezing them into a single table cell.

Appending | json to a read query switches the result panel from the usual table view to a text panel that pretty-prints the JSON payload and colorizes it with chroma.

SELECT metadata FROM users WHERE id = 1 | json

Also included: errors rendered into text panels are now styled (red, bold, padded) instead of being printed as plain text.

Changes

pkg/client/client.go

• New QueryType type with NormalQuery / JSONQuery values, plus a JSONSuffix (| json) constant.
• QueryResult gains two fields: QueryType and JSONData []byte.
• New trimJSONSuffix(query string) (string, bool) helper: reports whether a query requests the JSON view and returns the query with the suffix removed. Matching is case-insensitive (strings.EqualFold) and tolerant of surrounding whitespace, so | json, | JSON, | Json and | json are all recognized. Keeping this as a standalone function makes the parsing unit-testable without a database.
• AsyncQuery calls the helper on the read path, executes the stripped statement, and marks the result as a JSON query. QueryResult.Query keeps the original text including the suffix, so query history still shows what the user typed.
• JSON path validation, so failures are explained rather than producing garbage output:
  • the query must select exactly one column, otherwise the result carries an error saying how many columns were selected;
  • the column's database type must be JSON-compatible for the active driver;
  • an empty result set reports no data returned.
• New Client.isValidJSONColumn helper maps drivers to acceptable column types:
  • PostgreSQL: JSON, JSONB, TEXT, VARCHAR
  • MySQL: JSON
  • Oracle: JSON, CLOB, BLOB, VARCHAR2
  • SQL Server: NVARCHAR, VARCHAR, TEXT (no native JSON type)
  • SQLite: everything — it is dynamically typed, so json.Indent acts as the final validator
  • default: JSON, JSONB
• The existing row-scanning logic (BLOB handling, []byte → string conversion, etc.) is unchanged; it now lives under the default branch of a switch alongside the JSON branch.
• The read and exec paths now execute query (the goroutine's parameter, i.e. the suffix-stripped statement) instead of the q range variable. This is load-bearing rather than cosmetic: without it the | json suffix would reach the driver and every JSON query would fail with a syntax error.

pkg/bubbletui/resultset.go

• Registers a dblab-cyberpunk chroma style matching the app's palette: magenta keys, neon-green strings, purple numbers and literals, light-grey punctuation, red errors.
• On results, switches on qr.QueryType:
  • JSONQuery → json.Indent the raw bytes, highlight them with quick.Highlight(..., "json", "terminal256", dblab-cyberpunk), and render into a text panel.
  • NormalQuery → the existing table panel.
• Indent/highlight failures fall back to a styled error inside the same panel, so a malformed payload can't blow up the view.
• Query errors are now rendered through errorStyle before being set on the panel.

pkg/client/client_test.go

Seven cases added to ClientTestSuite, all driver-parameterized through DB_DRIVER like the rest of the suite. They rely on a jsonExpr helper that builds a driver-specific expression yielding a JSON-typed column (::jsonb on Postgres, CAST(... AS JSON) on MySQL, a plain literal on SQLite), so no schema change is required to exercise the feature.

Payloads are compared after json.Unmarshal rather than byte-for-byte, since jsonb reorders keys and MySQL compacts whitespace.

go.mod / go.sum

• Adds github.com/alecthomas/chroma/v2 v2.27.0 (and its github.com/dlclark/regexp2/v2 indirect dependency).

Fixes #251

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

The suite requires Docker (testcontainers):

make test                              # postgres
make test DB_DRIVER=mysql DB_USER=root

Both drivers pass.

Manual check in the TUI — no schema needed, this one literal exercises every token type in the style at once:

SELECT '{"name":"dblab","tags":["sql","tui"],"count":42,"ok":true,"extra":null}' AS doc | json

Verify:

• keys render magenta, strings green, numbers and true/null purple, punctuation grey;
• selecting more than one column reports the column-count error;
• selecting a non-JSON column reports the type error;
• a query matching no rows reports no data returned;
• queries without the suffix still render as tables.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings