* ci(lint): derive gate ceilings from merge-base counts and drop the budget files
The four lint gates (ruff strict, type discipline, basedpyright, test quality)
now fail a branch only when a rule's codebase count grows past its count at the
merge-base with litellm_internal_staging plus a fixed per-rule headroom, which
is zero everywhere except the LIT010/LIT011 and reportAny/reportExplicitAny
seeds. Base counts come from a disk cache, then the CI artifact the renamed
publish-lint-base-counts workflow uploads for every staging push (all four
checkers, one artifact per checker and sha), then a scan of the base worktree.
The four *-budget.json files, make lint-budget-update, budget_ratchet_check.py,
and the unratcheted check are gone, so no PR carries a budget edit again.
* test(lint-gates): assert checker identities by behavior and type the new gate tests
* test(lint-gates): resolve base points over an injected git so unit tests stay in-process
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Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
