Enable plugin registry installs by default (#6224)

* feat(plugins): enable registry installs by default

* fix(plugins): explain explicit Git source for missing registry IDs

* fix(plugins): tailor missing registry guidance to installation

* test(app): sample footer geometry in one browser frame

* fix(plugins): make registry source resolution deterministic

Directory existence must not change the meaning of a registry identifier shared by CLI, RPC, and UI installs. Classify explicit host paths in the source parser and explain recovery from registry transport and revision-selection failures.

* fix(plugins): recognize dot and Windows directory sources

* test(cli): wait for readable daemon ownership before cancellation

The cancellation test raced PID-file creation against its first write and parsed empty JSON in CI. Use the public daemon-instance reader to wait for and capture the supervisor PID before asserting cancellation cleanup.

* test(app): expect missing directory install guidance

public-docs/plugins/reference.md

@@ -2259,15 +2259,16 @@ failures stay inside the plugin error boundary.
 Paste one of these source identifiers into **Settings → Plugins**, or pass it to
 `paseo plugin install`. `paseo plugin add <source>` and `paseo plugin install <source>` are aliases.
 Absolute host paths are recommended because relative paths resolve against the daemon's working
-directory. The app does not expand `~`; your shell may expand it before the CLI runs.
+directory. The daemon expands `~` to its home directory.
 
 | Source                     | Accepted form                                                              | Example                                       |
 | -------------------------- | -------------------------------------------------------------------------- | --------------------------------------------- |
+| Plugin registry            | `owner/slug` or `host/owner/slug`                                          | `acme/review`                                 |
 | Host directory             | Absolute or relative path on the daemon host                               | `/srv/paseo/plugins/review`                   |
-| GitHub repository          | `github:owner/repository` or `owner/repository`                            | `github:acme/paseo-review`                    |
+| GitHub repository          | `git:owner/repository` or `github:owner/repository`                        | `github:acme/paseo-review`                    |
 | Git repository             | `git:<URL or SCP source>`; the prefix is optional for URLs and SCP sources | `git:https://git.example.com/acme/review.git` |
 | npm package                | `npm:<name>[@<version, tag, or range>]`; `npm:` is optional                | `npm:@acme/paseo-review@^1.2.0`               |
-| Plugin below a source root | Append `:relative/plugin/path` to any source                               | `github:acme/monorepo:plugins/review`         |
+| Plugin below a source root | Append `:relative/plugin/path` to a directory, Git, or npm source          | `github:acme/monorepo:plugins/review`         |
 
 Git URLs use `https://`, `http://`, `ssh://`, `git://`, or `file://`. SCP sources use
 `user@host:path`. `file://` selects Git acquisition, not directory installation.
@@ -2283,24 +2284,27 @@ The package registry validates the selected version, tag, or range.
 
 Paseo resolves an identifier in this order:
 
-1. An existing directory matching the complete identifier on the daemon host wins, including a
-   literal directory containing `:`.
+1. A bare `owner/slug` is a registry id; local directory sources are `.` or `..`, or start with `./`, `../`, `.\`, `..\`, `/`, `~`, a Windows drive (`C:\` or `C:/`), or a UNC (`\\server\share`) prefix.
 2. Otherwise, recognize `npm:`, `github:`, or `git:` before interpreting a subdirectory suffix.
    `git://` is a Git URL scheme. An explicit prefix selects acquisition of that kind.
 3. Recognize a final `:relative/plugin/path` only when its suffix contains no empty, `.` or `..`
    segments. A lone `.` selects the source root. Both `/` and `\` separate suffix segments; use `/`
    across hosts. URL ports and the separator in an SCP source stay part of the source. A suffix
    that does not satisfy these rules stays part of the identifier.
-4. Without an explicit prefix, an existing directory matching the remaining source wins.
-5. Resolve Git URLs and SCP sources as Git; expand exact `owner/repository` shorthand to GitHub
-   HTTPS. `github:` requires that shorthand; `git:` accepts it as well as URLs and SCP sources.
-6. Resolve a remaining npm package name with its optional selector through the host's registry.
+4. Resolve bare `owner/slug` through the default plugin registry and `host/owner/slug` through
+   that registry host. Resolve Git URLs and SCP sources as Git. `github:` requires
+   `owner/repository` shorthand; `git:` accepts it as well as URLs and SCP sources.
+5. Resolve a remaining npm package name with its optional selector through the host's registry.
    Reject anything else.
 
-Plugin registry installs are off by default. When the daemon enables them with
-`pluginRegistryEnabled: true` or `PASEO_PLUGIN_REGISTRY_ENABLED=1`, bare `owner/slug` and
-`host/owner/slug` resolve through the plugin registry instead of GitHub, the registry record owns
-the revision and plugin path, and GitHub shorthand requires `github:`.
+The default registry is `https://plugins.paseo.sh`. Browse [published plugins](https://paseo.sh/plugins)
+and install with `paseo plugin add owner/slug`. Registry records own the revision and plugin path.
+Use `git:owner/repository` for explicit GitHub shorthand or a full Git URL.
+Set `PASEO_PLUGIN_REGISTRY` to use a self-hosted default URL, including a path prefix.
+Private registry credentials use `pluginRegistries: { "host": { "authorization": "Bearer token" } }`
+in daemon config. Restart the daemon after changing these startup settings. Credentials go only
+to that registry, never to artifact hosts or redirects. Installed plugins retain their recorded
+source and registry URL when defaults change.
 
 Directory lookup happens on the daemon host. The app uses the `paseo-plugin.json` ID; the CLI
 accepts `--id <runtime-id>` to override it. An existing installation ID is rejected without changing
@@ -2347,9 +2351,10 @@ deletes its managed files; removing a directory plugin keeps your source directo
 paseo plugin init /absolute/path/to/plugin
 paseo plugin install /absolute/path/to/plugin
 paseo plugin install /absolute/path/to/plugin --id another-runtime-id
-paseo plugin add owner/repository
+paseo plugin add owner/slug
+paseo plugin add git:owner/repository
 paseo plugin add https://git.example.com/owner/repository.git --ref main
-paseo plugin add owner/monorepo:plugins/review
+paseo plugin add git:owner/monorepo:plugins/review
 paseo plugin ls [id]
 paseo plugin update <id>
 paseo plugin update --all --check