Release prep for the nine reliability/scaling PRs merged today (#105, #106,
#107, #108, #109, #115, #117, #134) so the merge can be tagged and published.

docs/TUNING.md is the deployment sizing guidance from the benchmarking campaign
behind 1.6.0/1.6.1, now that the config comments reference it. Two updates
before committing it: a note for the new MINHASH_MATCHING_MAX_PAIRS budget
(including that the function batch size remains an upper bound alongside it),
and its caveat about the performance options not being released yet, which
stopped being true in 1.6.1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>