[Interactive Graph] Add WB Announcer to Ray graph

[catandthemachines]

Summary:

Wires the Ray graph's movePoint (endpoint) and moveRay (whole-line grab
handle) actions into the existing WB Announcer pipeline.

What this PR does:

• Reducer: case "ray" in doMovePointInFigure now emits
  stateAnnouncement: {type: "move-ray-point", pointIndex, x, y} when an
  endpoint moves. case "ray" in doMoveLine emits
  stateAnnouncement: {type: "move-ray-line", coords} when the whole ray is
  dragged via the grab handle. Both case "ray" blocks are split out from
  the shared case "linear"/case "vector" blocks so linear and vector
  are intentionally untouched.
• Types: adds MoveRayPointAnnouncement and MoveRayLineAnnouncement to
  InteractiveGraphStateAnnouncement.
• Screen reader text: getAnnouncementText handles "move-ray-point" by
  index — the endpoint (index 0) uses srRayEndpoint ("Endpoint at X comma
  Y.") and the terminal point (index 1) uses srRayTerminalPoint
  ("Through point at X comma Y.") — and "move-ray-line" uses
  srRayGrabHandle ("Ray with endpoint X1 comma Y1 going through point X2
  comma Y2.").
• Component: adds an optional ariaLive override prop to MovableLine. It
  defaults to undefined, preserving the internal aria-live state machine
  for the other graphs that still share MovableLine (linear, segment,
  linear-system). ray.tsx passes ariaLive="off" so the WB Announcer is
  the only source of move announcements for the Ray graph.
• TODOs reference LEMS-4189,
  which tracks removing aria-live from useControlPoint and MovableLine
  once every line graph's reducer is wired to the announcer.
• Tests: adds reducer tests for movePoint and moveRay on ray, adds
  screenreader-text tests (move-ray-point at both indices +
  move-ray-line), and removes the now-obsolete "Should update the
  aria-live when X is moved" test from ray.test.tsx.

Note: the ariaLive override prop on MovableLine is the same shared
infrastructure introduced in the Linear PR (#3683). This PR re-introduces
it identically so the two can merge in either order with a trivial /
no-op conflict on movable-line.tsx.

Issue: LEMS-4199

Test plan:

Automated

• pnpm tsc — passes
• pnpm lint packages/perseus — passes
• pnpm jest packages/perseus/src/widgets/interactive-graphs — passes

Manual (reviewer)

• Open the Interactive Graph → Ray story in Storybook (pnpm storybook). Turn on VoiceOver / NVDA (or use the Storybook a11y addon's live-region inspector).
• Tab to the ray's endpoint handle. Confirm the initial focus announces "Endpoint at X comma Y." (from aria-label, unchanged).
• Press arrow keys to move the endpoint one snap step at a time. Confirm:
  • You hear "Endpoint at X comma Y." after each move (new WB Announcer payload).
  • You do not hear the announcement twice. Before this PR, both the endpoint's aria-live and the WB Announcer would have fired.
• Tab to the terminal point (the point the ray passes through). Confirm moves announce "Through point at X comma Y.".
• Tab to the ray itself (the whole-line grab handle). Press arrow keys to drag the ray. Confirm you hear "Ray with endpoint X1 comma Y1 going through point X2 comma Y2." after each keyboard drag — this is the new move-ray-line announcement, and you should hear it only once.
• Regression: open the Linear, Segment, and Linear System stories and confirm they still announce moves the same way they did before (their behavior is unchanged in this PR).

[github-actions]

Size Change: +216 B (+0.04%)

Total Size: 506 kB

📦 View Changed

Filename	Size	Change
packages/perseus/dist/es/index.js	199 kB	+216 B (+0.11%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	20.6 kB
packages/keypad-context/dist/es/index.js	1 kB
packages/kmath/dist/es/index.js	6.32 kB
packages/math-input/dist/es/index.js	98.5 kB
packages/math-input/dist/es/strings.js	1.61 kB
packages/perseus-core/dist/es/index.item-splitting.js	12.1 kB
packages/perseus-core/dist/es/index.js	26.1 kB
packages/perseus-editor/dist/es/index.js	105 kB
packages/perseus-linter/dist/es/index.js	9.41 kB
packages/perseus-score/dist/es/index.js	10.2 kB
packages/perseus-utils/dist/es/index.js	403 B
packages/perseus/dist/es/strings.js	8.55 kB
packages/pure-markdown/dist/es/index.js	1.39 kB
packages/simple-markdown/dist/es/index.js	6.71 kB

_{compressed-size-action}

[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (9daa827) and published it to npm. You
can install it using the tag PR3685.

Example:

pnpm add @khanacademy/perseus@PR3685

If you are working in Khan Academy's frontend, you can run the below command.

./dev/tools/bump_perseus_version.ts -t PR3685

If you are working in Khan Academy's webapp, you can run the below command.

./dev/tools/bump_perseus_version.js -t PR3685