ui(sql-workspace): Session menu for autocommit, statement timeout, Begin and Preferences (#1150)

[ZhuchkaTriplesix]

Refs #1150

Changes

• The autocommit switch, the statement timeout dropdown and the settings button become one Session ▾ menu (QueryaActionMenu). The menu shows the autocommit state and, for the timeout, the current value with a check mark.
• Menu entries: Autocommit on/off, the timeout values, Begin transaction (while no transaction is open), Preferences. The values and handlers are the ones used before.
• The transaction badge and the inline Commit / Rollback from the previous change stay as they are.

Not in this PR

• The one-row layout: the query tab caption and the Data Output bar still exist, Diagram is still in the toolbar, and the results toolbar has no elapsed time.
• Run group and editor group with icon buttons (History, Format, Open, Save).
• Widget tests for the menu entries and the one-row layout at 800 px.

[github-actions]

Grid scroll benchmark

metric	base	PR	change
p50	11.72 ms	13.63 ms	+16.3% ⚠️
p90	27.51 ms	23.16 ms	-15.8%
p99	48.72 ms	49.42 ms	+1.4%
stutters	322.00	280.00	-13.0%

Informational only (threshold 5%). Shared CI runners are noisy; re-run before trusting a single result.

[github-actions]

Grid scroll benchmark

metric	base	PR	change
p50	13.85 ms	14.59 ms	+5.3% ⚠️
p90	17.07 ms	20.69 ms	+21.2% ⚠️
p99	36.68 ms	45.16 ms	+23.1% ⚠️
stutters	332.00	324.00	-2.4%

Informational only (threshold 5%). Shared CI runners are noisy; re-run before trusting a single result.