P0-X: Rename proximity graph types from Metroid* to SemanticNeighbor*

[Copilot]

"Metroid" was being used for the sparse proximity/neighbor graph, colliding with its correct meaning: the dialectical search probe { m1, m2, c }. This blocks MetroidBuilder from being implemented cleanly.

Renamed symbols

Before	After
MetroidNeighbor	SemanticNeighbor
MetroidSubgraph	SemanticNeighborSubgraph
putMetroidNeighbors	putSemanticNeighbors
getMetroidNeighbors	getSemanticNeighbors
getInducedMetroidSubgraph	getInducedNeighborSubgraph
needsMetroidRecalc	needsNeighborRecalc
flagVolumeForMetroidRecalc	flagVolumeForNeighborRecalc
clearMetroidRecalcFlag	clearNeighborRecalcFlag

IndexedDB schema (DB_VERSION 2 → 3)

Object store metroid_neighbors renamed to neighbor_graph. The v3 upgrade handler creates neighbor_graph as a fresh store — no migration logic, as there is no installed base.

Files changed

• core/types.ts — interface renames
• storage/IndexedDbMetadataStore.ts — implementation + schema version bump
• tests/Persistence.test.ts — updated call sites and type annotations
• tests/SalienceEngine.test.ts — updated MetadataStore stub methods

Original prompt

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This section details on the original issue you should resolve

<issue_title>P0</issue_title>
<issue_description>All P0 tasks, issues and sub issues belong here, either directly or by reference. Please subtask every issue with P0 in its name for ease of tracking.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes P0 #66

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[Copilot]

Pull request overview

Resolves an architectural naming collision by renaming the proximity/neighbor graph (“Metroid*” misnomer) to “SemanticNeighbor*”, freeing “Metroid” for the { m1, m2, c } dialectical probe concept and aligning storage schema naming accordingly.

Changes:

• Renames proximity graph types and MetadataStore methods from Metroid* to SemanticNeighbor*.
• Bumps IndexedDB schema version to v3 and renames the object store metroid_neighbors → neighbor_graph with an upgrade-time migration.
• Updates unit tests and test stubs to use the new types/method names.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
core/types.ts	Renames exported proximity-graph types and MetadataStore API methods.
storage/IndexedDbMetadataStore.ts	Implements renamed APIs; bumps DB_VERSION to 3; adds v2→v3 cursor migration to neighbor_graph.
tests/Persistence.test.ts	Updates round-trip tests to use SemanticNeighbor* naming and new APIs.
tests/SalienceEngine.test.ts	Updates MetadataStore mock stubs to match renamed method names.