Add Sensing action_control block to bind keys for movement/actions

[tracygardner]

Motivation

• Provide a way in the Sensing category to bind keyboard keys to high-level actions (FORWARD/BACK/LEFT/RIGHT/BUTTON1-4) using a camera-style grid key picker, matching the existing Camera key-bind UX.

Description

• Added a new Blockly block action_control (blocks/sensing.js) that shows an action dropdown plus a grid key picker and appears next to action_pressed in the Sensing toolbox (toolbox.js, locale/en.js).
• Added generator support so action_control emits setActionKey(action, key) at generation time (generators/generators.js).
• Implemented runtime APIs in api/sensing.js: setActionKey(action, key) and getActionKeys(action), and updated actionPressed(action) to consult custom keys plus defaults; updated whenActionEvent to use getActionKeys so events and booleans stay in sync.
• Added persistent runtime state flock.actionKeyMap and initialization/reset hooks in flock.js, and added translation strings and tooltip text for the new block (locale/en.js).

Testing

• npm run build completed successfully on the branch (bundle built).
• npm run lint failed due to pre-existing lint issues in flock.js that are unrelated to this change (reported by the linter).
• npm run test:api failed in this environment because Playwright’s browser binaries are not installed (environment limitation), not because of the change.
• Ran the dev server and an automated Playwright script to open the page and capture the toolbox UI; a screenshot showing the new action_control block in Sensing was produced at artifacts/action-control-sensing.png.

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Codex Task