Keep Smart recall consistent across merged projects

Smart search, timeline context, and selected observation details now use the same checkout project scope. An observation found through a merged project alias remains available in the next two steps, instead of incorrectly returning “not found.”

• Resolves the same project read keys for search results, explicit timeline anchors, query-selected timeline anchors, and selected observation reads.
• Keeps adopted records visible while excluding unrelated or unadopted records and respecting platform-source filters.
• Preserves the Smart default three-step workflow and the optional dumb_search alternative introduced in 15.0.0. No API or schema migration is required.

Regression coverage includes real HTTP/SQLite cases that fail on 15.0.0 and pass with this repair, plus related scope-isolation checks.