chore(release): bump version to 0.19.0 - #541

Summary

Release for the work landed in this session:

• [build] strip dependency debug info, add clean-stale, fix pre-push hook path bugs #538 — target-cache-size management (dependency debug-symbol stripping, cargo xtask clean-stale, pre-push hook fixes)
• [build] fix Windows CI timeout from dependency opt-level override #539 — fix for a Windows CI timeout regression introduced by [build] strip dependency debug info, add clean-stale, fix pre-push hook path bugs #538
• [mcp] Cursor progress-notification override + structural completion gate #540 — Cursor progress-notification override (force_progress_notifications) + structural completion-gate guidance (SPEC R2.5.5, server instructions, /ahma skill), completing the 6-phase await-timeout redesign (phases 0-4 landed previously via feat(mcp): override the per-client request budget; warn on unrecognized clients #534-refactor(mcp): collapse the per-client request budget into one fallback constant #537)

cargo xtask bump-version 0.19.0: Cargo.toml, Cargo.lock (workspace member versions only — no dependency changes), skills/ahma/SKILL.md, scripts/install.sh, scripts/install.ps1.

Test plan

• cargo deny check (full) — advisories/bans/licenses/sources all ok
• Local pre-push guardrail suite (fmt, clippy-equivalent checks, version consistency, license boundaries, smoke test) passed end-to-end