Query execution UX: cancel/spinner fixes, target-tab support, run-status glyphs

CHANGELOG.md

@@ -12,6 +12,8 @@ All notable changes to QueryDen are documented here. This project adheres to [Se
 
 ### Fixed
 - **[#217](https://github.com/openidle-dev/queryden/issues/217) — Running a query now gives instant feedback and can't be triggered twice.** Pressing `Ctrl+Enter` previously showed no "running" state until *after* the database connection handshake (`Database.load`), which can take seconds on a cold connection — so the editor looked idle and a second press would run the query again. `setIsExecuting(true)` now fires synchronously at the start of execution (the spinner and tab status glyph appear the instant you press the shortcut), and a re-entrancy guard drops a duplicate trigger while a run is already in flight.
+- **Cancelling a query no longer freezes query execution.** The re-entrancy guard added in #217 keys off `isExecutingRef`, which every code path cleared on completion — except `cancelQuery`, which only flipped the visible spinner off. Because libpq has no real query cancel, the in-flight `db.select` keeps running server-side and only clears the flag when it eventually returns, so after pressing **Cancel** the toolbar showed "Run" but the guard silently swallowed every subsequent run and the results bar never came up. `cancelQuery` now clears the executing flag immediately (and bumps the execution generation so the abandoned run no-ops on its late return instead of clobbering whatever ran after the cancel).
+- **The "running" spinner now stays on the tab that launched the query.** Execution state was a single global `isExecuting` flag, and every indicator (the tab status glyph, the SQL Editor header bar, the results-panel loading state) was gated on `activeTabId === tab.id` — so the spinner painted onto whichever tab was *active* and appeared to "follow" you when you switched tabs, even though a different tab owned the running query. A new `executingTabId` records which tab actually started the run: the tab glyph is keyed to that tab, and the editor header / psql window / results-panel loading only show "running" when the active tab is the executing one. (The top toolbar's Run/Cancel control stays global, since QueryDen runs one query at a time and you can cancel it from anywhere.)
 - **You can now close the last remaining query tab.** The tab close button was hidden whenever only one tab was open, leaving no way to close the final editor. The button is always available now; closing the last tab falls back to the empty-state launcher.
 - **PSQL Console error messages no longer flash and disappear.** Errors in the CLI execution path (PostgreSQL version unknown, download cancelled, download failed, psql not found, `\watch` errors) are now committed as persistent `psqlConsoleEntry` entries before the live-output grace period expires, preventing the output from going blank after 300ms. The `\watch` loop-end path also commits accumulated output. Fixes Windows WebView2 race where `showLiveGrace` expired without entries.
 - **"Open in Explorer" now works reliably on Windows.** Empty tabs no longer silently fail — the auto-save directory is resolved as a fallback parent path. All catch blocks now show toast feedback (`showToastMessage`) instead of silent failure.