feat(schema): add DOOH structured selling-unit fields to placements

[garvitkaushik-123]

Summary

Implements #5537 — adds structured DOOH selling-unit metadata to placements so buyers can evaluate screen characteristics during product discovery.

• dooh_placement_attributes object on both placement.json and placement-definition.json with four optional fields:
  • slot_duration_seconds — duration of one ad slot
  • loop_duration_seconds — full loop rotation (canonical source, supersedes pricing-layer field)
  • screen_resolution — physical { width, height } in pixels
  • motion — full_motion, partial_motion, or static (new dooh-motion-type enum)
• identifiers[] array on both placement schemas — reuses the { type, value } pattern from property identifiers for DOOH venue_id, screen_id, openooh_venue_type, etc.
• dooh-motion-type.json enum — full_motion, partial_motion, static
• identifier-types.json title updated from "Property Identifier Types" to channel-neutral "Identifier Types"
• flat-rate-option.json loop_duration_seconds description updated with superseded note
• Docs — DOOH placement attributes section added to media-products.mdx

Design decisions

• Follows the existing channel-overlay pattern (video_placement_types, audio_distribution_types, etc.) — new fields sit alongside those in the same position
• additionalProperties: true on dooh_placement_attributes to allow future field additions without breaking changes
• identifiers[] is channel-neutral by design — reuses the same enum already used for property identifiers
• motion enum values align with industry conventions (OpenOOH/OAAA terminology)

Test plan

• All 4232 unit tests pass
• TypeScript typecheck passes
• Schema build (build:schemas) succeeds
• Verify DOOH placement example validates against updated schema

Closes #5537

[aao-release-bot]

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[bokelley]

This contribution still appears directionally useful, but it has been idle since June and main plus the active 3.2 OOH work have moved substantially. Please confirm you want to continue and rebase/reconcile it with the current OOH contract. If there is no response by August 17, we will close it as stale; the work can be reopened when an implementer is ready to carry it.

[garvitkaushik-123]

Hey @bokelley — yep, still on this! Got sidetracked but I'm picking it back up now. I see main has moved quite a bit with the 3.2 OOH work and the static OOH draft (#6146) — will rebase and reconcile over the next few days. Should have it updated well before the 17th.

[garvitkaushik-123]

Rebased onto current main. No conflicts — the placement schema additions (identifiers[], dooh_placement_attributes) slot in after the social_placement_surfaces block that landed since June.

Reviewed the static OOH draft (#6146) — that work is architectural for classic/printed OOH and doesn't overlap with the DOOH selling-unit fields here. The dooh_placement_attributes pattern stays consistent with the existing channel-overlay approach (video_placement_types, audio_distribution_types, etc.).

No schema shape changes from the original — just a clean rebase. Ready for review whenever it makes sense in the 3.2 cycle.