feat: add Herdr plugin for ghzinga links

[osolmaz]

Opened on behalf of Onur Solmaz (osolmaz).

Summary

Herdr can now hand GitHub issue and pull request links to ghzinga.
The plugin stays thin: Herdr calls gzg herdr-plugin open/viewer, and ghzinga owns the URL parsing, pane reuse, session naming, and Herdr pane control in Rust.
This matters because the ghzinga-specific behavior now ships with ghzinga instead of living in plugin shell scripts.

What Changed

The production path is now Herdr manifest wiring into ghzinga-owned Rust entrypoints.
The plugin opens or reuses a right-side ghzinga pane next to the clicked pane, using Herdr's current Ctrl-click link-handler surface.

• Added plugins/herdr/herdr-plugin.toml with a GitHub issue/PR link handler, one action, and one viewer pane.
• Added hidden Rust commands: gzg herdr-plugin open and gzg herdr-plugin viewer.
• Moved URL normalization, source-pane scoped session naming, pane reuse validation, and Herdr CLI pane open/focus logic into ghzinga Rust.
• Removed production open.sh and viewer.sh; shell remains only in test fakes/harnesses.
• Documented install, architecture, Ctrl-click behavior, and verification in README.md and plugins/herdr/README.md.
• Added fake Herdr tests and a live Herdr smoke test for the side-pane flow.
• Updated capture manifests after validating the existing captures still match the current app output.

Testing

I tested the Rust-owned path directly, with fake Herdr, and inside a real disposable Herdr session.
The live Herdr smoke starts Herdr, links the plugin, opens a right-side pane, and verifies ghzinga rendered fixture content there.

• cargo test herdr_plugin --lib
• plugins/herdr/test/test-open.sh
• plugins/herdr/test/test-viewer.sh
• scripts/herdr-plugin-live-smoke.sh
• npx -y @simpledoc/simpledoc check
• PATH="/tmp/ghzinga-py312/bin:$PATH" scripts/ci-local.sh

The first local scripts/ci-local.sh run used macOS system Python 3.9.6 and failed on existing Python 3.10+ type syntax in capture scripts.
The full gate passed after putting a temporary Python 3.12 venv first on PATH, matching the Python version available on GitHub's ubuntu-latest runner.

Risks

The main limitation is Herdr's current trigger surface.
The plugin handles Ctrl-click link events; plain left-click link routing would need Herdr itself to expose that behavior to plugins.

• gzg must be installed on PATH for normal Herdr plugin launches.
• The plugin uses Herdr 0.7.0 plugin/link-handler/pane CLI APIs, so future Herdr API drift is the main compatibility risk.
• GHZINGA_BIN is supported for local development or custom viewer launches, but normal installs should not need it.

[osolmaz]

Final implementation report

Summary:

• Added the Herdr plugin under plugins/herdr with a GitHub issue/PR link handler, open action, and viewer pane.
• The plugin opens a right-side ghzinga pane next to the source pane and reuses that pane for later links from the same source pane/session.
• Added plugin docs, root README install notes, shell tests, CI wiring, and an isolated live Herdr smoke test.

Validation passed:

• codex review --base main: no actionable correctness issues on the latest head.
• tmpdir=$(mktemp -d); uv venv --python 3.12 "$tmpdir/venv" >/dev/null; PATH="$tmpdir/venv/bin:$PATH" scripts/ci-local.sh: passed.
• scripts/herdr-plugin-live-smoke.sh: passed. It starts a real Herdr session in a PTY, links the local plugin in isolated Herdr XDG dirs, invokes the link-handler action with Herdr-style env, verifies a right-side ghzinga pane opens, and verifies fixture content renders.
• herdr plugin install dutifuldev/ghzinga/plugins/herdr --ref feat/herdr-plugin --yes with isolated Herdr XDG dirs and inherited Herdr socket env cleared: passed at commit af4c77dae7277b7be9891c7115f4c9f15211f785.
• gh pr checks 39: verify passed.

PR comments/reviews:

• No PR issue comments, reviews, or inline review threads were present when checked.

[osolmaz]

Final implementation report for the current Rust-owned Herdr plugin implementation.

Summary:

• Herdr plugin manifest lives in plugins/herdr/herdr-plugin.toml and is installable from dutifuldev/ghzinga/plugins/herdr.
• Production plugin logic is owned by ghzinga Rust entrypoints: gzg herdr-plugin open and gzg herdr-plugin viewer.
• The plugin handles GitHub issue/PR links, opens a right-side ghzinga plugin pane beside the source pane, reuses that pane for later links from the same source pane/session, and validates that a stored pane still belongs to dutifuldev.ghzinga before reuse.
• No production shell scripts remain in the plugin path; shell is only used for tests and live smoke harnesses.

Validation passed on head 71f9702af782280040191afd1eaf998f080796b3:

• cargo test herdr_plugin --lib
• plugins/herdr/test/test-open.sh
• plugins/herdr/test/test-viewer.sh
• scripts/herdr-plugin-live-smoke.sh against real Herdr 0.7.0: linked the local plugin, opened a right-side ghzinga pane from a live Herdr session, and verified rendered fixture content.
• npx -y @simpledoc/simpledoc check
• PATH="/tmp/ghzinga-py312/bin:$PATH" scripts/ci-local.sh
• codex review --base main: no actionable correctness issues.
• GitHub Actions verify: passed.

PR comments/reviews:

• No issue comments, reviews, or inline review threads are pending.

Known Herdr-side limitation:

• Current Herdr link handlers are invoked by Ctrl-click. Plain left-click behavior would require a Herdr change; ghzinga documents this limitation.

[osolmaz]

Follow-up fix for nested ghzinga panes:

• Links clicked from inside a ghzinga Herdr viewer now reuse that same viewer instead of opening another side pane.
• New viewer panes write a reverse pane-to-session mapping for deterministic reuse.
• Existing viewer panes opened by older builds are also handled: if the reverse mapping is missing, the plugin validates the source pane is this plugin's viewer and falls back to ghzinga's Herdr pane-context session resolution.

Additional validation passed on head 011e83fdcb41446e6f19685ed0f866ceb3e77f96:

• cargo test herdr_plugin --lib
• plugins/herdr/test/test-open.sh
• plugins/herdr/test/test-viewer.sh
• scripts/herdr-plugin-live-smoke.sh verified a real Herdr side pane and confirmed an internal link kept the pane count unchanged.
• Manual active-Herdr check from current ghzinga pane w1:pE: workspace pane count stayed 2 -> 2, and ghzinga reported focused openclaw/openclaw#81834.
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings
• npx -y @simpledoc/simpledoc check
• GitHub Actions verify: passed.

[osolmaz]

Follow-up fix for stale restored tabs in Herdr plugin viewers:

• gzg herdr-plugin viewer now launches ghzinga with --new --session <stable-plugin-session> <target>.
• This keeps the stable session/control socket needed for later gzg open --session ... updates, but prevents a newly created Herdr side pane from restoring tabs left behind by a previous closed plugin pane.
• The live smoke now keeps restore/control enabled in the viewer and verifies an internal link to a different issue fixture updates the same pane.

Validation passed on head 1e84a126d091a3de891af4e66129c7f5d17f120a:

• cargo test herdr_plugin --lib
• plugins/herdr/test/test-viewer.sh
• plugins/herdr/test/test-open.sh
• scripts/herdr-plugin-live-smoke.sh
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings
• npx -y @simpledoc/simpledoc check
• GitHub Actions verify: passed.