fix(herdr): seed mouse_capture=false so select-to-copy works under code-server

[gitricko]

Root cause

Inside hermes-webtop, Hermes is served through code-server (a browser web terminal). In a herdr pane, drag-select-to-copy to the system clipboard silently fails.

• herdr defaults to mouse_capture = true, which intercepts pane mouse (SGR) events so xterm.js never gets the drag — native selection never starts.
• herdr defaults to copy_on_select = true, auto-copying each selection via OSC 52. Per herdr release note #2015, the OSC 52 clipboard fix is scoped to VS Code Remote Tunnels ONLY, not code-server. So 0.7.4 (baked into the image, PR feat(docker): bake herdr + tmux into webtop image #38) is on the broken path.

The fix

Set ui.mouse_capture = false in herdr's config. This hands the mouse back to xterm.js and restores native select/copy. Setting copy_on_select = false alone is insufficient (the drag is still herdr-captured, nothing copies), so the fix is mouse_capture = false only.

Implementation

Added docker/start-herdr.sh (auto-copied into /custom-cont-init.d/ by the Dockerfile's COPY *.sh). It:

• Sources common.sh, runs under runuser -l abc (matching the other seed scripts).
• Gates on first boot only: seeds /config/.config/herdr/config.toml only if it does not already exist, so an existing user config is never overwritten on restart / image update.
• Writes the exact [ui] TOML block (with the explanatory comment) and runs herdr config check to validate; skips the check gracefully if the binary is not yet on PATH at seed time.
• Runs ensure_ownership on the config dir and logs a skip on second run.

Trade-off

Disabling mouse_capture turns off herdr's right-click context menu and click-to-focus pane features. In the webtop (always browser-served) this is acceptable in exchange for working select-to-copy. Desktop/local herdr users are unaffected — this config is webtop-specific.

Verification

• bash -n docker/start-herdr.sh passes.
• Seed test wrote a config that herdr config check reports as config: ok and that contains mouse_capture = false; TOML parses cleanly.
• Idempotent: second run logs [start-herdr] config already present, skipping and does not overwrite.
• git diff --stat shows only docker/start-herdr.sh added.

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