fix(ui): the action key inventory lists disabledReason - #26859

Part of #26619. This is a main-red hotfix for the spec half (#26786). The console half is still the PR that closes the card.

Clause-②: no
Metadata-protocol: none
Skills-docs: none (a test-inventory row, no authoring surface)

维护者速读

• 改了什么： ui/packages/core 的 SPEC_ACTION_KEYS 补上一行 disabledReason。
• 为什么改： feat(spec): a greyed action says why — disabledReason beside disabled #26786 给 ActionSchema 加了 disabledReason，但 objectui 的动作键清单没跟上，actionKeys.pin.test.ts 在 main 上报 missing ['disabledReason']，Test UI 红，所有合并 main 的分支都受影响。
• 风险与回滚： 一行数据，只影响「是否算未知键」的判断。回滚就是 revert 本 PR。
• 需要你做的： 无，席位落地。

What changes

• ui/packages/core/src/actions/actionKeys.ts: SPEC_ACTION_KEYS gains 'disabledReason' after 'disabled'. The list restates every key the spec's ActionSchema declares, and feat(spec): a greyed action says why — disabledReason beside disabled #26786 added that key. An action that carries it is no longer counted as having an unknown key.
• .changeset/26619-action-keys-disabled-reason.md: @object-ui/core patch. (The root .changeset, which the changeset gate counts; ui/.changeset is the imported objectui directory.)

Why

actionKeys.pin.test.ts compares SPEC_ACTION_KEYS with the keys of the built ActionSchema. Since #26786 merged (13dc413f), it fails on main with missing: ['disabledReason']. That turns Test UI red on main (8eef9a8d) and on every branch that merges main. The failure was reproduced by another card's dev (standing-down comment 6450604330 on PR #26831).

Verification

• The failure was read on main 8eef9a8d: the pin's missing set is ['disabledReason'] and nothing else.
• The UI workspace dependencies are not installed in this container, so the pin was not run locally. CI's Test UI on this head is the check.

Human Minimum

• 1. Schemas start as Zod; packages/spec holds no runtime logic. (packages/spec is not touched.)
• 2. Every name I added uses the casing for its kind.
• 3. No formatter ran; pnpm lint passes.
• 4. One issue, one branch off an up-to-date main, one pull request.
• 5. A change that publishes carries a changeset, and both declaration lines are filled in here and in the changeset.
• 6. packages/spec touched: its generated artifacts are regenerated and committed. (Not touched.)
• 7. No hand edits to content/docs/references/, packages/*/CHANGELOG.md or content/docs/releases/.
• 8. Title, body and comments are in English (apart from the maintainer quick-read block).
• The Before Submitting list in CONTRIBUTING.md is done.

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