merge-commit-backup: Merge origin/main into ethie/oh-god (pluginify refactor reconciliation)
Reconciles the "pluginify everything" refactor (moving provider adapters, platform adapters, and terminal backends out of core into plugins/) with 267 commits of main. main had 515 edits across 635 files; our branch moved 98 files into plugins/. The dangerous class was main editing files at OLD paths that we relocated — handled below. STRUCTURAL DECISIONS ai-gateway + vercel_sandbox: honored main's PR #33067 deletion. Dropped our orphaned plugins/terminals/vercel/ dir and all 3 stale vercel refs that survived in pyproject (workspace member, [all] entry, uv source). tools/lazy_deps.py: kept mai...