fix(internal): apply QuotedIdentifier in more cases

[PadenZach]

Add test cases to test for these, fixes #270

Example of this fixing the issue:

Summary by type:
  tables: 1 to modify

Tables:
  ~ ex
    ~ ID (column)

DDL to be executed:
--------------------------------------------------

ALTER TABLE ex ALTER COLUMN "ID" TYPE bigint;

Do you want to apply these changes? (yes/no): yes

Applying changes...
time=2026-01-30T15:31:41.750-06:00 level=DEBUG msg="Attempting database connection" host=localhost port=5432 database=postgres user=postgres sslmode=prefer application_name=pgschema
time=2026-01-30T15:31:41.765-06:00 level=DEBUG msg="Database connection established successfully"
time=2026-01-30T15:31:41.765-06:00 level=DEBUG msg="Executing SQL" description="set search_path to target schema" sql="SET search_path TO example, public"
time=2026-01-30T15:31:41.766-06:00 level=DEBUG msg="SQL execution succeeded" description="set search_path to target schema"
Set search_path to: example, public

Executing group 1/1...
  Executing 1 statements in implicit transaction
time=2026-01-30T15:31:41.766-06:00 level=DEBUG msg="Executing SQL" description="execute 1 statements in group 1" sql="ALTER TABLE ex ALTER COLUMN \"ID\" TYPE bigint;;"
time=2026-01-30T15:31:41.778-06:00 level=DEBUG msg="SQL execution succeeded" description="execute 1 statements in group 1"
Changes applied successfully!

[Copilot]

Pull request overview

Fixes incorrect SQL generation when table columns use quoted identifiers (e.g., "ID"), ensuring generated ALTER/COLUMN COMMENT statements quote identifiers consistently (addresses #270).

Changes:

• Quote column identifiers in ALTER COLUMN statements (type/default/nullability changes).
• Quote column identifiers in COMMENT ON COLUMN statements (both create-time and alter-time).
• Add golden diff test cases for ALTER COLUMN + column comments with quoted identifiers.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/diff/column.go	Applies ir.QuoteIdentifier to column names in generated ALTER TABLE ... ALTER COLUMN ... statements (including USING expressions).
internal/diff/table.go	Applies ir.QuoteIdentifier to column names in generated COMMENT ON COLUMN ... statements (create + alter paths).
testdata/diff/create_table/alter_column_quoted_identifier/old.sql	Adds baseline schema for quoted-column type-change test.
testdata/diff/create_table/alter_column_quoted_identifier/new.sql	Adds target schema for quoted-column type-change test.
testdata/diff/create_table/alter_column_quoted_identifier/diff.sql	Golden expected diff SQL for quoted-column type-change.
testdata/diff/create_table/alter_column_quoted_identifier/plan.sql	Golden expected plan SQL output for quoted-column type-change.
testdata/diff/create_table/alter_column_quoted_identifier/plan.txt	Golden expected human-readable plan output for quoted-column type-change.
testdata/diff/create_table/alter_column_quoted_identifier/plan.json	Golden expected JSON plan output for quoted-column type-change.
testdata/diff/comment/column_comment_quoted_identifier/old.sql	Adds baseline schema for quoted-column comment test.
testdata/diff/comment/column_comment_quoted_identifier/new.sql	Adds target schema for quoted-column comment test.
testdata/diff/comment/column_comment_quoted_identifier/diff.sql	Golden expected diff SQL for quoted-column comment.
testdata/diff/comment/column_comment_quoted_identifier/plan.sql	Golden expected plan SQL output for quoted-column comment.
testdata/diff/comment/column_comment_quoted_identifier/plan.txt	Golden expected human-readable plan output for quoted-column comment.
testdata/diff/comment/column_comment_quoted_identifier/plan.json	Golden expected JSON plan output for quoted-column comment.

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[tianzhou]

LGTM. Thank for the contributions