[P1][UI-01] UI intermediate representation and validator

Programme: #1
Epic: #19

## Objective
Define a safe declarative UI IR so AI can create interfaces without executing arbitrary privileged code.

## Scope
- Versioned component tree with stable component/object IDs.
- Data bindings to workspace/entity/query state and explicit action capability references.
- Layout, typography, density and accessibility metadata.
- Trusted components for text/media/forms/actions; sanitize rich content.
- Resource limits: tree depth, component count, text/media sizes, update frequency and external-resource policy.
- Validator for schemas, bindings, source visibility, accessibility names/roles and action targets.
- Version migration and deterministic serialization for portable workspace apps.

## Security rules
- No arbitrary JavaScript/native code in the trusted UI IR.
- External media/network loads count as egress and require policy-compatible sources.
- A control cannot appear actionable unless it references a resolvable capability/action contract.
- Generated content cannot impersonate trusted shell/approval chrome.

## Acceptance criteria
- [ ] Invalid schemas, dangling bindings and unknown component versions fail before rendering.
- [ ] Unauthorized or unresolvable action controls are rejected/disabled before installation.
- [ ] Privilege-bearing script/native-code payloads are impossible through the standard IR.
- [ ] Accessibility metadata is required for interactive components.
- [ ] Resource-limit adversarial layouts fail without freezing the shell.
- [ ] Same approved IR renders deterministically from the same bound state.

## Dependencies
- CORE-01
- SEC-02

**First phase:** P1
**Maturity target:** P2
**Owner:** workspace-ui-data

## Task issues
- [ ] #402 `UI-01.T01` — Define component and binding schema
- [ ] #403 `UI-01.T02` — Implement structural and resource validation
- [ ] #404 `UI-01.T03` — Validate data and source bindings
- [ ] #405 `UI-01.T04` — Validate actions against real capabilities
- [ ] #406 `UI-01.T05` — Require accessible and trustworthy semantics
- [ ] #407 `UI-01.T06` — Compile validated views and migrations
- [ ] #408 `UI-01.T07` — Fuzz and snapshot the UI contract

Start with the task issues #402–#408 and review dependencies CORE-01 and SEC-02 before taking on the parent design. Use the acceptance criteria to define completion: invalid, unsafe, inaccessible, nondeterministic, or resource-exhausting UI IR must be rejected before rendering or installation.

Written by the indexing model from the issue text.