docs: add the issue-sources spec (favorites, views, filters)

I drafted a design for unifying Pearl's fetch surface around sources: read the viewer's Linear favorites and run them by type-dispatch behind one pearl-pick-source picker, with the per-dimension filters as the primitives favorites resolve into and the ad-hoc builder as the exploratory fallback. It fixes the by-project me-lock and resolves label and user favorites by stable id, which needs two small filter-compiler forms (:label-id, :assignee-id). The Linear favorites schema is verified against the live API and Codex's review is incorporated, so the spec is Ready.

0 files changed, 0 insertions, 0 deletions