fix: remove non-portable askpass bridge; rely on native git credentials

The askpass bridge bound a Unix-domain socket to a vault filesystem path
(net.createServer().listen(...sock)). That is invalid on Windows, where
Node's listen() expects a named pipe, so publish aborted with
'listen EACCES: permission denied ...askpass.sock' before git ever ran —
even when the user's git could authenticate. The bridge was non-portable in
general (Windows named pipes; the helper script needs a node binary on PATH).

Remove the bridge and let the user's system git handle credentials via its
native helpers (Git Credential Manager / osxkeychain / libsecret) for https
and ssh-agent for ssh — the 'store nothing' model we already chose.
GIT_TERMINAL_PROMPT=0 stays so git fails fast instead of hanging, and
publish errors now include a credential/identity hint. Deletes askpass.ts
and its test (3 tests); suite 32/32, tsc clean, build OK.

Co-Authored-By: Claude

README.md

@@ -42,11 +42,12 @@ An Obsidian plugin that publishes the active note as a Jekyll blog post via git.
 
 ## Credentials model
 
-The plugin uses your **system git** binary for all remote operations. No passwords or tokens are stored inside Obsidian or the plugin's data files.
+The plugin uses your **system git** binary for all remote operations and stores **no** passwords or tokens inside Obsidian or the plugin's data files. Authentication is delegated entirely to git's own credential handling, which works across platforms:
 
-When git needs a credential (e.g. HTTPS password or a personal access token), an **askpass bridge** intercepts the prompt and shows a native Obsidian modal so you can type the value. The value is passed directly to git through a temporary socket and is never persisted.
+- **HTTPS remotes** — git uses your configured credential helper: **Git Credential Manager** (bundled with Git for Windows), **osxkeychain** (macOS), or libsecret (Linux). The first push prompts you through that helper's own dialog and caches the result in your OS keychain. If no helper is configured, the publish fails fast with a clear message (the plugin sets `GIT_TERMINAL_PROMPT=0` so git never hangs waiting on a non-existent terminal).
+- **SSH remotes** — git uses your existing SSH agent / `~/.ssh` key configuration. Use an `ssh://` URL and make sure your key (or agent) is set up; no extra steps in the plugin.
 
-For SSH remotes, the plugin relies on your existing SSH agent or `~/.ssh` key configuration — no extra steps needed.
+Commits are authored with the **Author name/email** from the plugin settings if set; otherwise git uses your machine's git identity (`user.name` / `user.email`). If neither is configured, git will refuse to commit — set an author in settings or configure a global git identity.
 
 ## Development