v0.2.1 — dependency refresh and a pinned Go 1.26.5 toolchain

No API change: the only files touched since v0.2.0 are go.mod and go.sum.

Pins toolchain go1.26.5, whose standard library fixes the x509 issues
govulncheck flagged against 1.26.0. A consumer does not inherit that pin
-- Go only honours the main module's toolchain line -- so each service
sets its own; this keeps the library's own builds and tests on it.

Dependencies move up with it: modernc.org/sqlite 1.54 -> 1.55, plus
patch bumps to libc, x/sys and go-isatty.