chore(release): prepare 0.16.1

[jleni]

Summary

Version bump for the 0.16.1 release. Ships since v0.16.0:

Cacheability, C/C++ units that previously always missed:

• feat(cc): key ring's Darwin debug flag -gfull via the resolved probe #860 feat(cc): key ring's Darwin debug flag -gfull via the resolved probe
• feat(cc): key cc-rs's Apple debug flag -gdwarf-2 via the resolved probe #851 feat(cc): key cc-rs's Apple debug flag -gdwarf-2 via the resolved probe
• fix(cc): cache zstd builds using -fmerge-all-constants #861 fix(cc): cache zstd builds using -fmerge-all-constants
• fix(cc): classify -fsanitize-undefined-strip-path-components=-1 so aws-lc-sys 0.44 jitterentropy TUs cache (#840) #845 fix(cc): classify -fsanitize-undefined-strip-path-components=-1 so aws-lc-sys 0.44 jitterentropy TUs cache (cc: cache aws-lc-sys jitterentropy builds using -fsanitize-undefined-strip-path-components=-1 #840)
• fix(cc): cache compiles carrying -mno-omit-leaf-frame-pointer #842 fix(cc): cache compiles carrying -mno-omit-leaf-frame-pointer (cc: cache debug builds using -mno-omit-leaf-frame-pointer #839)
• fix(cc): cache trivial auto var pattern init #850 fix(cc): cache trivial auto var pattern init

Correctness:

• fix(rustc): key all outcome-affecting lint configuration #834 fix(rustc): key all outcome-affecting lint configuration
• fix(key): accept duplicate native search paths #852 fix(key): accept duplicate native search paths
• fix(key): survive non-UTF-8 environments and multi-byte leak windows #829 fix(key): survive non-UTF-8 environments and multi-byte leak windows
• fix(daemon): treat remote import failures as misses #841 fix(daemon): treat remote import failures as misses
• fix(service): use indexed identity for planner upserts #832 fix(service): use indexed identity for planner upserts

Robustness:

• fix(store): use advisory build locks #854 fix(store): use advisory build locks
• fix(daemon): drain accepted handlers on shutdown #847 fix(daemon): drain accepted handlers on shutdown
• fix: close the remaining majors from the main review (refcounts, purge locking, async flocks, TUI restore) #830 fix: close the remaining majors from the main review (refcounts, purge locking, async flocks, TUI restore)
• chore(deps): refresh OpenDAL and security patches #836 chore(deps): refresh OpenDAL and security patches

Also in the tree but not user-visible: docs rewrite (#863), OpenDAL and Lance nightly benchmarks (#864, #859), CODEOWNERS for private-runner workflows (#862), test and CI work (#855, #853, #846, #833, #831).

Patch bump: #860 and #851 are labelled feat, but both only add flag keying that turns previously-uncacheable translation units into cacheable ones. No API or behaviour change.

Note: crates/kache-proofs moves from 0.0.0 to 0.16.1. That crate landed in #855 after the last bump, so this is the first time cargo set-version --workspace has swept it up. It is publish = false and outside the consistency gate, same as kache-e2e and kache-service, which already track the workspace version.

After merge: tag v0.16.1 on the merge commit to trigger the release.

Checklist

• Version bumped in workspace + crates + Helm chart (same shape as chore(release): prepare 0.16.0 #828)
• just bump 0.16.1 (cargo set-version --workspace, lock settled by cargo check)
• scripts/check-version-consistency.sh passes: kache == kache-core == kache-core dep-pin == 0.16.1
• cargo check --workspace clean