docs: complete 0.1.6 maintenance notes

[steipete]

Summary

• make the 0.1.6 (Unreleased) changelog cover the already-landed Go networking and tooling module updates
• record the pnpm and GitHub Actions maintenance already present on main

Risk

Low. Documentation only; no runtime, build, version, or release behavior changes.

Proof

• git diff --check
• exact current-main Go 1.25.11 unit, race, vet, lint, govulncheck, tidy-diff, GoReleaser config, six-target cross-build, native CLI, and Docker smoke proof passed before this documentation-only closeout
• autoreview clean: no accepted/actionable findings

[steipete]

Landed as e19ab32fa5d8ea750bc46572e95223d7d47cad3f.

Tested on exact PR head bbbfe6ad174b8c9c5639f8aa1a2b99a0c94500dd:

• git diff --check
• autoreview clean: no accepted/actionable findings
• exact-head Linux/macOS/Windows tests, race coverage, lint, govulncheck, Docker, and GitGuardian all green: https://github.com/steipete/blucli/actions/runs/28522289744 and https://github.com/steipete/blucli/actions/runs/28522289723

This was documentation-only. The documented maintenance batch had already passed pinned Go 1.25.11 unit/race/vet, tidy-diff, six-target builds, GoReleaser validation, native CLI proof, and an exact Docker smoke test on the merged predecessor commit.