fix(editor): quote PostgreSQL table completion identifiers

[mikevillari]

PostgreSQL table suggestions currently insert catalog names verbatim, so accepting My_Schema_With_Caps.My_Table_With_Caps produces unquoted SQL that PostgreSQL folds to lowercase. This also reproduces with the completion provider from before #715 (base 4c5f657).

Follow-up to @nktnet1's report in #705: #705 (comment).

Pass the editor's existing connection dialect into the completion provider and use the shared identifier quoter for PostgreSQL table-name components. Keep labels/filtering separate from inserted SQL, preserve qualified replacement ranges and bare-label fallback, and recognize quoted table names when offering columns after a dot. Re-register when the connection dialect changes. Other dialects keep their existing table insertion behavior.

Tests assert applied edits for mixed-case schema/table names, typed qualifiers, dot-triggered suggestions, bare labels, embedded quotes, spaces, reserved words and lowercase names; they also cover quoted column lookup and dialect changes in the editor.

Testing

• Seven new applied-edit cases failed before the fix; they pass afterward. Two quoted column-lookup regressions also failed before the lookup change and pass afterward.
• Focused provider regression selection: 23 pass, 0 fail.
• Complete isolated component runner: all 35 groups passed, including the new dialect-switch regression.
• Format, lint, typecheck, knip, chart/check, channels/showcase/check, readme/check and security/check passed. Lint retains existing warnings.
• Production build and library build passed.
• bun run test: 11,143 pass, 197 fail in the initial unit/API/integration stage; 191 were chart tests requiring missing Helm, four packaging tests require missing 7-Zip, and two were the quoted-column regressions subsequently fixed and rerun green in the focused selection. The chained later stages therefore did not run through this command; components were run separately above. No full-suite or full-coverage pass claimed. Browser E2E and live PostgreSQL were not run locally; CI remains the merge gate.

This uses the provider's existing dot-delimited table-label representation. It does not redesign schema metadata or add support for completing partially quoted input or quoting column suggestions.

AI-assisted implementation and validation.

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[cevheri]

I need your local test results regarding the following points:

1. PostgreSQL tables can be defined entirely in uppercase or lowercase (e.g., user_authority / USER_AUTHORITY) and must be queryable without quotes.
2. Tables might have been created with mixed-case names enclosed in quotes (e.g., "UserAuthority").
3. The table might reside in the public schema or a different schema (e.g., public.orders, authschema.users).

[mikevillari]

Verified locally against a real PostgreSQL 18.4 process, using the exact PR head 0a53b7e25c2dfc3d4018043dcf01fd6088a1f02f. No code change was needed for these cases.

Results: 36 autocomplete-generated queries passed, plus 21 control queries with the expected outcomes.

I created each of these in public, authschema, and additionally a quoted mixed-case schema "AuthSchema":

CREATE TABLE identifier	Name stored in the catalog	Unquoted table references	PR autocomplete result
lowercase_table	lowercase_table	lowercase and uppercase both work	quoted exact catalog name; query succeeds
UPPERCASE_TABLE	uppercase_table	lowercase and uppercase both work	"uppercase_table"; query succeeds
"MixedCaseTable"	MixedCaseTable	fail with SQLSTATE 42P01, as expected	"MixedCaseTable"; query succeeds
"QUOTED_UPPER_TABLE"	QUOTED_UPPER_TABLE	fails with SQLSTATE 42P01, as expected	"QUOTED_UPPER_TABLE"; query succeeds

The important distinction in point 1 is how the table was created: unquoted CREATE TABLE USER_AUTHORITY stores user_authority, so both unquoted spellings resolve. Explicitly quoted CREATE TABLE "USER_AUTHORITY" creates a different, case-sensitive name that requires quotes. This PR quotes the name returned by the catalog; it does not make previously valid unquoted SQL invalid. It does insert optional quotes for ordinary lowercase catalog names.

Example queries actually generated and executed:

SELECT marker FROM "lowercase_table";
SELECT marker FROM "uppercase_table";
SELECT marker FROM public."MixedCaseTable";
SELECT marker FROM "authschema"."MixedCaseTable";
SELECT marker FROM "AuthSchema"."QUOTED_UPPER_TABLE";

For both public and authschema, controls also executed fully unquoted queries such as SELECT marker FROM public.UPPERCASE_TABLE and SELECT marker FROM authschema.lowercase_table successfully.

Method: create isolated fixture tables containing distinct marker rows; read their names from information_schema.tables; construct the cache with the same display-name convention as postgres.ts:1478 (bare name for public, schema-qualified otherwise); bundle and call this PR's actual registerSQLCompletionProvider; apply its returned replacement range and insertText; execute the resulting SQL and assert the exact expected marker. Covered empty-prefix selection, partially typed names, explicit public qualifiers, and non-public schema-dot suggestions. Used a modeled Monaco word/range interface, not the browser UI or the full database-provider connection flow. The pre-existing public-schema-dot popup and partially quoted input were not claimed as covered.

Server reported: PostgreSQL 18.4 on x86_64-apple-darwin24.6.0, compiled by Apple clang version 17.0.0, 64-bit. This was a temporary local native PostgreSQL server, not an in-memory SQL substitute. The server was stopped and its database removed after verification. AI-assisted execution and reporting.