Release v0.19.1: fix subagent navigation

[oribarilan]

Summary

Fixes #79 and prepares the v0.19.1 patch release.

• Pass navigation keys to OpenCode in read-only child-session views without changing the Vim mode. Both host entrypoints use the same controller; the Vim engine is unchanged.
• Correct v2 ancestry metadata so root prompts remain editable. Add regressions for child navigation, Composer ownership, and normal/visual/insert mode preservation.
• Pin the headless keymap test dependency in devDependencies so clean installs do not rely on locally installed optional peers.
• Add development navigation aliases, bump package.json and VERSION to 0.19.1, and update release notes and current package refs. Preserve v0.19.0 history and the documented legacy v1 pin.

This branch starts from current main, rather than reopening the already-merged v2 support branch.

Validation

• Fresh Bun install: just check passed lint and 355 tests.
• just compat-unit: 16 tests passed.
• Cache-installed v0.19.1 on OpenCode 1.18.33: cold/warm loading and 39 exact-state checks passed.
• Cache-installed v0.19.1 on OpenCode 2.0.15: cold/warm loading and 48 exact-state checks passed.
• Independent port/release review found no issues. Manual v1/v2 smoke checks were also completed before the version bump.

The host suites retain the two inherited tab-offset and snapshot-redo known gaps. The eight pre-existing typecheck errors are unchanged. V2 support remains experimental and bounded to the tested host versions; this release does not claim full parity or support for every v2 release.

Closes #79.