feat(editors): expose block_id and action_id behind an Advanced toggle

[StephenTangCook]

Closes #152.

What

Every block editor now ends with a collapsed ▸ Advanced disclosure holding that block's Block ID. Each button form gets the same disclosure for its Action ID:

• actions block buttons (actions-editor)
• section button accessory (section-editor)
• card action buttons (card-editor, also reused per card by the carousel editor)

Both ids were previously reachable only by hand-editing the JSON drawer, even though the builder generates a random action_id for every button it inserts. Clearing a field drops the key so Slack goes back to generating one.

How

One shared AdvancedIdField in field.tsx, built on a native <details> element. No React state, no icon, no new dependency: the disclosure triangle, the toggle, and the keyboard/screen-reader behavior all come from the browser.

Block ID lives in block-editor.tsx, the single component every context window renders through, so all 19 block types pick it up at once.

Not included

input blocks and context_actions blocks already show their element action_id as a normal visible field. Left alone rather than hidden behind the new toggle, since they already solve the reported problem and demoting them would be a regression in discoverability.

Verification

• New unit test test/block-editor-advanced.test.tsx covers editing block_id, editing a button action_id, and clearing back to undefined.
• Full suite green: 331 unit tests, 117 Storybook play tests, typecheck, biome.
• Checked end to end in the demo app: setting a button's Action ID to approve_request lands in the exported Block Kit JSON.

🤖 Generated with Claude Code

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[StephenTangCook]

Bumped @tightknitai/slack-block-kit-validator to 0.1.13 on this branch, which lands the fix for slack-block-kit-validator#66: duplicate action_id within a block is now flagged. That gap was reachable precisely because this PR makes the field editable, so the two belong together.

Confirmed in the demo. Two buttons sharing action_id: "123" now surface:

Block 1: Buttons
elements[1].action_id must be unique within the block — '123' appears at elements[0] and elements[1]

New test in test/duplicate-ids.test.ts covers both directions: duplicates inside one block are reported and attributed to that block, while the same id in two different blocks stays valid, since state.values is keyed block_id then action_id.

Unrelated to this PR but worth knowing: duplicate block_id on two markdown blocks is still intentionally not flagged, because Slack drops block_id on markdown blocks. On any other block type it errors.