docs(api): TRA-799 — remove asset current-location from the API docs

[mikestankavich]

Docs-only companion to platform PR trakrf/platform#384 (TRA-799). The platform change makes an asset's current location fact data, not a dimension attribute the asset resource carries. This PR brings docs/api/ in line with that contract.

Three contract changes documented

1. Asset response shape — location_id / location_external_key are removed from the asset resource. GET /api/v1/assets and GET /api/v1/assets/{asset_id} return master data only. Current location is read from GET /api/v1/reports/asset-locations or GET /api/v1/assets/{asset_id}/history.
2. Asset write — location_id / location_external_key in a POST or PATCH body are rejected 400 / code: read_only on presence. The prior PATCH accept-if-matches / reject-if-differs handling is retired — with location off the read shape there is nothing to echo.
3. Asset list filter — the ?location_id / ?location_external_key filters are removed from GET /api/v1/assets. Filter by location on /reports/asset-locations instead.

The reporting endpoints (/reports/asset-locations, /assets/{id}/history) are unchanged — they remain the system of record for asset location.

Files changed

• data-model.md — asset detail view dropped from the scan-data consumption table; POST/PATCH rejection prose unified.
• resource-identifiers.md — the page used asset location_* as its primary teaching example for FK-pair, present-as-null, accept-if-matches, and list-filter patterns; those examples are re-anchored on LocationView.parent_* and the /reports/asset-locations row. Paired-key matrix reworked.
• pagination-filtering-sorting.md — /assets location filter removed from the param table, mutual-exclusion rule, repeatable-filter examples, validator prose, and worked example.
• quickstart.mdx, errors.md, design-notes.md — corrected sentences that framed asset location_* as a read-shape / accept-if-matches field.
• changelog.md — new v1.0 entry; prior entries (BB40, BB63) left as historical record.

The OpenAPI-driven /api interactive reference is generated from the platform-synced spec and updates with that sync — not hand-edited here. Design spec + plan included under superpowers/.

Verification

• pnpm build passes — no broken internal links or anchors.
• git grep audit: every remaining location_id / location_external_key hit is a path parameter, a parent_* reference, a LocationView field, or a /reports/asset-locations / history row — none describes an asset response field or an /assets list filter.
• Edited docs files are Prettier-clean (errors.md carries pre-existing, unrelated Prettier drift from main, left untouched).

🤖 Generated with Claude Code

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