Send a node's emit pulse round the rim instead of scaling it out

The ring hung off the node itself, and `inset` on an absolute child
resolves against the padding box — so on the brain's thick status ring it
landed inside the outer edge and painted over the status the ring carries.
Both node shapes now hang it off a border-less wrapper, where the same
offsets clear the rim whatever border the node draws (measured: 4px on all
four sides, on a 1px card border and a 7px neuron ring alike).

The shape is a conic-gradient arc masked to the padding band, running one
lap in `--duration-pulse` and going out on the way past.

Note: BrainNode.tsx also carries an unrelated in-flight change from a
concurrent session (the `seen` ref gating the pulse on a real emit); the
two could not be separated in one file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

NOTEPAD.md

@@ -38,7 +38,6 @@ should reopen it.
 - CHORE/UI: a streaming edge's dashes sit inside the `prefers-reduced-motion: no-preference` guard, so a reduced-motion user gets no streaming indicator at all. Lifting `stroke-dasharray` alone out of the guard keeps the static signal without the motion.
 - CHORE/UI: only node-to-node edges carry the streaming dash. `endpoints.ts` builds a dashboard endpoint's edges without the producing port's `stream` flag, so a training loss feeding a chart — the case the march was drawn for — is still a plain line.
 - CHORE/UI: the Home flow-activity table's name cell is `max-w-0` with nothing setting a floor, so `demo_training` reads as "demo⋯" at 1440px while the row has slack to spare. The cap is what keeps the table from widening the page; it wants a minimum beside it.
-- CHORE/UI: `.node-pulse`'s `inset: -3px` resolves against the padding box, so on a thick border it lands inside the outer edge and paints over the status ring rather than sitting one ring outward as its comment claims. Measured on a 9px border — the comment and the geometry disagree.
 - FEAT/UI (deferred until MCP lands): add a "bot" icon button to the home view (graph panel) which opens a chat window (reuse general concept of a side panel like in flows/nodes to make it a chat panel which can open on any screen (stacks below any other existing panel -> introduce stacking) to give support on errors/write code, generate dashboards etc) to explain the error(s)
 - FEAT/UI make the header (Fluksio - YEAR) and the logo in the sidebar link to the main page (fluksio.com)
 - FEAT/UI consider adding a diagram to the Home view which shows a histogram of the different classes of nodes and which time it takes to execute (logarithmic scale); this should give a hint on the load and help to detect bottle necks/hotspots