chore(lint): clear all no-unused-vars warnings (position-precise)
Removed/renamed the remaining 39 unused locals/dead code, file-by-file:
- unused destructured bindings/params (remove the binding, keep the call)
- unused single-line pure consts and dead functions/interfaces removed
- deleted the dead _FeedItem component and its now-unused imports
- amber _readChunks self-call fixed; SpotMap popup call site updated
Warnings: 182 -> 7 (only react-refresh/only-export-components remain).
no-explicit-any=0, exhaustive-deps=0, no-unused-vars=0.
Gate: 101 tests, 0 errors, boot smoke green. AGENTS.md baseline + guidance updated.
6def78fffe