feat(layer): add canonical composer query preview widget

[ty13r]

Summary

• Rebases feat(layer): add canonical composer query preview widget #129 onto main and replaces the product-specific composer_inline_ask shape with canonical composer_query_preview.
• Registers the widget as a first-class :layer_shell_and_callout primitive across unified_iur, unified_ui, live_ui, Ash UI adapters, authoring validation, docs, and specs.
• Uses canonical UnifiedIUR.Interaction transport for dismiss/open/save actions; renderer-only phx-* attrs are generated at the Live UI boundary.
• Keeps the preview as a sibling primitive above/near a composer, not a chat_composer slot.

Architecture Decisions

• Canonical name: composer_query_preview, with no repo/product-specific names in the canonical contract.
• Trigger model: parent/runtime owns data flow and mounts the preview with state; no imperative product-specific helper is required here.
• Finding IDs: opaque id values in canonical output; old finding_id input is normalized only for compatibility.
• Actions: dismiss/open/save are canonical interactions (:close, :open, :command) instead of on_* callback fields.
• Shortcut/UI hints: not canonicalized as product constants; renderers can decide presentation locally.
• Family: :layer_shell_and_callout, matching the existing rail/callout primitives.

Verification

• mix format --check-formatted on touched Elixir files
• Focused canonical widget test set: 90 tests, 0 failures
• Spec-listed Ash UI boundary/adapter tests: 51 tests, 0 failures
• Renderer/docs/admission tests: 46 tests, 0 failures
• bash ./scripts/validate_specs_governance.sh
• bash ./scripts/validate_guides_governance.sh
• bash ./scripts/validate_code_docs.sh
• git diff --check -- . ':(exclude)_build/**' ':(exclude)deps/**'

Notes

• mix spec.next is not wired in this checkout (The task "spec.next" could not be found).
• Bare mix format --check-formatted still requires explicit files/patterns in this repo; the touched-file format check passed.
• Full mix test ran 1059 tests with 1 existing unrelated failure: missing traceability matrix entry for REQ-WFPS-006 in AshUI.Phase8IntegrationTest.