lore-overlay: extraction — move the staging spike to the rac-overlay repo

[tcballard]

Sub-issue of #321 (lore-overlay, ADR-093).

Corpus: Initiative 2 (extraction half) of rac/roadmaps/lore-overlay.md; repo slug ratified in ADR-100 (per ADR-092 rac-* naming).

Scope:

• Create itsthelore/rac-overlay and move the staging spike (lore-overlay/ on the PR feat(overlay): add the Lore capture overlay MVP (verified core + Tauri shell scaffold) #202 branch: the tested Rust capture core + the Tauri shell scaffold) with history preserved — the develop-in-repo-then-extract pattern used for the VS Code extension. Maintainer org action.
• No rac-core engine change; the app is a thin client over the rac contract (ADR-063).
• When the extraction lands, close PR feat(overlay): add the Lore capture overlay MVP (verified core + Tauri shell scaffold) #202 as superseded-by-extraction (its README's verified-vs-not framing carries over).
• Product name stays a working title; Lore brand at org/marketplace level.

Tick on #321 when the code builds in its own repo and PR #202 is closed.