Target: cultlib-gaps, the standing home for capabilities consumers find missing

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/cultlib-gaps-target.md

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+# CultLib Gaps: Target
+
+Date: 2026-10-09. Campaign `cultlib-gaps` in the Eureka mind.
+
+## Why
+
+Consumers of CultLib keep finding capabilities a reasonable consumer of a general
+library would expect and that CultLib lacks. Doctrine says a gap is filled in its
+owner, never worked around in the consumer. This campaign is the standing home for
+those gaps, so each one lands in CultLib as a small cut instead of a local helper in
+whichever project hit it.
+
+Known gaps at opening (each a follow-up in the mind, owned by the consumer campaign
+that found it):
+
+- CultMath `BoundedLeastSquares.Solve` has a fixed KKT tolerance (1e-6); Aetheria's
+  thrust allocator needs a tighter one (`aetheria-release:follow_up:cultmath-bls-kkt-tolerance`).
+- `cultcache-rs` has no decimal type, its snapshot reads follow symlinks, and its
+  single-file store stages files with the process umask and no mode option
+  (`eureka-body:follow_up:cultcache-rs-decimal-and-nofollow`).
+
+## Invariants
+
+- `owner-fills-gap`: a capability a consumer needs from CultLib is added to CultLib, with the consumer adopting it; no consumer-local copy survives the cut that adds it.
+- `defaults-unchanged`: a new option defaults to today's behaviour; existing callers and stored bytes do not change.
+- `wire-parity`: a CultCache wire change keeps byte parity across runtimes against the C# reference, with a cross-runtime fixture.
+- `semver-measured`: a public API change bumps the package version by measured semver and ships as a tagged release consumers can pin.
+
+## Not in scope
+
+- Growing CultCache into a general database (memory `cultcache-scope-restraint`).
+- Any consumer's adoption code beyond the pin bump; that stays in the consumer's campaign.