Let one effect own the flow canvas viewport

Three things moved the viewport independently — the shape-fit effect, focusNode,
and React Flow's own fitView prop — so a fourth for "centre the node I just
selected" would have been a fourth party to the argument. There is one effect
now, and which branch it takes is decided by what changed rather than by what is
true: selecting a node brings that node into the lane the panel leaves, and
every other change — new wiring, a new endpoint, a panel opening — re-fits the
whole flow into the same lane. A selection centres once, so the port edits that
follow re-fit around it, which is what makes a new edge's far end visible.

The refit triggers on the edge count, not the bindings key: that key changes on
every keystroke in a message-name field, and refitting per character is not what
"an edge was created" means.

renderedNodes overwrote xyflow's own `selected` flag, so a box-selection of
several nodes was invisible even though delete and copy acted on all of them.

The logs panel was a popover anchored on its own button, which is why it sat off
centre, hugged the button and closed on any outside click. It is a plain surface
above the dock now, and the button is stateful. Escape still closes it.

Expanding a node's editor gives the panel the whole inset and puts the code on
the left with the settings beside it, while the toolbar and the flow name
translate off screen. Narrowing the window past `md` gives the room back — the
sheet it becomes has no second column to hold.

The zoom buttons are gone: there is a mouse, or there is a pinch.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uq8mtNb97A7praJLyeEYgs

frontend/tests/runtime.spec.ts

@@ -92,9 +92,29 @@ test("the logs panel shows what a node printed and why one failed", async ({
   await page.getByTestId("run-flow").click()
   await page.getByTestId("flow-logs").click()
 
-  const panel = page.locator('[data-slot="popover-content"]')
+  const panel = page.getByTestId("logs-panel")
   await expect(panel).toContainText("sensor read 21.5 degrees")
   await expect(panel).toContainText("RuntimeError")
+
+  // Reading the logs is something you do *while* working on the flow, so a
+  // click on the canvas leaves them up — only the button or Escape closes it.
+  await page.locator(".react-flow__pane").click({ position: { x: 8, y: 8 } })
+  await expect(panel).toBeVisible()
+
+  // It sits above the dock rather than on it, and shares its centre. The dock
+  // has no box of its own to measure, so its span is its first and last
+  // buttons; its padding is symmetric, so their midpoint is its centre.
+  const logs = (await panel.boundingBox())!
+  const dock = (await page.getByTestId("run-flow").boundingBox())!
+  expect(logs.y + logs.height).toBeLessThan(dock.y)
+
+  const first = (await page.getByTestId("add-node").boundingBox())!
+  const last = (await page.getByTestId("publish-flow").boundingBox())!
+  const centre = (first.x + last.x + last.width) / 2
+  expect(Math.abs(logs.x + logs.width / 2 - centre)).toBeLessThan(2)
+
+  await page.getByTestId("flow-logs").click()
+  await expect(panel).toBeHidden()
 })
 
 test("a flow can be paused and let go again", async ({ page }) => {