Merge train 4843-11b (CI only; not for merge)

[erikdarlingdata]

Merge train, not for merge. This PR exists only to run CI once. Its branch is train 10b (#5177, not landed yet) plus the squash of each PR below, in this order, so CI here covers dev + train 10b + train 11b. After train 10b lands, each PR below is squash-merged by itself in the same order, and dev's final tree is checked against this branch's tree. Then this PR is closed unmerged. It replaces #5176.

Part of #4966 and #4843.

PRs in this train, in order

• WEB: the PostgreSQL tabs' window aggregates and trend grids say where their data starts (part of Say where the data starts on every time-ranged tab, in Lite and both Darling viewers #4966) (WEB: the PostgreSQL tabs' window aggregates and trend grids say where their data starts (part of #4966) #5165)
• MCP: Darling's blocking, deadlock and long query tools say where their data starts (part of Say where the data starts on every time-ranged tab, in Lite and both Darling viewers #4966) (MCP: Darling's blocking, deadlock and long query tools say where their data starts (part of #4966) #5171)
• Web line charts get a menu: copy/save image, export CSV, show data source, reset zoom (Web line charts get a menu: copy/save image, export CSV, show data source, reset zoom #5166)
• get_server_trend: latch, spinlock, session stats and collector duration trends (get_server_trend: latch, spinlock, session stats and collector duration trends #5170)
• Web Top Queries: the desktop grid's 45 columns, grouped, with a detail=full read for the fields the page lacked (Web Top Queries: the desktop grid's 45 columns, grouped, with a detail=full read for the fields the page lacked #5169)

Train head 68f25798c, tree 31233a7ac, stacked on train 10b 833f04770. A local merged-tree check ran 1,585 tests, including the whole guard family. The one failure is a class that cannot load on macOS.

[erikdarlingdata]

Superseded by train 11c, which drops one member whose source-text pin turned this run red. Closing unmerged.