Onboard onto bakery: bakery.toml + dev/beta/release CI, relocate content paths

Adds bakery.toml (binaries, license_file, desktop_file, data_archive for
the guide content directory) and the standard three-track CI workflows,
mirroring the pattern used across the rest of the bread ecosystem.

Also fixes the tour/troubleshooting-symptoms loaders (tour.rs,
troubleshoot.rs) to check the bakery-writable user content root
(~/.local/share/breadhelp/content) before the system path a pacman
package would have used — the main ContentStore already did this via
user_content_root(), these two were the last holdouts still hardcoded to
/usr/share/breadhelp only.

src/content/mod.rs

@@ -41,7 +41,7 @@ pub struct ContentStore {
     guides: Vec<Guide>,
 }
 
-fn user_content_root() -> PathBuf {
+pub(crate) fn user_content_root() -> PathBuf {
     if let Ok(xdg) = std::env::var("XDG_DATA_HOME") {
         let p = PathBuf::from(xdg);
         if p.is_absolute() {

src/content/tour.rs

@@ -86,15 +86,26 @@ struct TourFile {
 }
 
 const SYSTEM_TOUR_PATH: &str = "/usr/share/breadhelp/content/tours/onboarding.toml";
+const TOUR_SUBPATH: &str = "tours/onboarding.toml";
 
+/// Checks the user content root first (where bakery installs content —
+/// see `content::user_content_root`), falling back to the system path a
+/// pacman package would have used. Same "user copy wins" precedent as
+/// `ContentStore::load`.
 pub fn load() -> Vec<Step> {
-    let Ok(text) = std::fs::read_to_string(Path::new(SYSTEM_TOUR_PATH)) else {
+    let user_path = super::user_content_root().join(TOUR_SUBPATH);
+    let path = if user_path.exists() {
+        user_path
+    } else {
+        Path::new(SYSTEM_TOUR_PATH).to_path_buf()
+    };
+    let Ok(text) = std::fs::read_to_string(&path) else {
         return Vec::new();
     };
     match toml::from_str::<TourFile>(&text) {
         Ok(f) => f.steps,
         Err(e) => {
-            eprintln!("breadhelp: {SYSTEM_TOUR_PATH} failed to parse: {e}");
+            eprintln!("breadhelp: {} failed to parse: {e}", path.display());
             Vec::new()
         }
     }

src/content/troubleshoot.rs

@@ -36,13 +36,11 @@ struct SymptomFile {
 }
 
 const SYSTEM_SYMPTOMS_DIR: &str = "/usr/share/breadhelp/content/troubleshooting/_symptoms";
+const SYMPTOMS_SUBPATH: &str = "troubleshooting/_symptoms";
 
-/// Loads every `*.toml` file in the symptoms directory, keyed by file stem so
-/// a `SymptomOption::goto` of `"no-sound:check-mute"` can be resolved.
-pub fn load_all() -> std::collections::HashMap<String, Vec<SymptomNode>> {
-    let mut out = std::collections::HashMap::new();
-    let Ok(entries) = std::fs::read_dir(Path::new(SYSTEM_SYMPTOMS_DIR)) else {
-        return out;
+fn scan_symptoms_dir(dir: &Path, out: &mut std::collections::HashMap<String, Vec<SymptomNode>>) {
+    let Ok(entries) = std::fs::read_dir(dir) else {
+        return;
     };
     for entry in entries.flatten() {
         let path = entry.path();
@@ -62,5 +60,16 @@ pub fn load_all() -> std::collections::HashMap<String, Vec<SymptomNode>> {
             Err(e) => eprintln!("breadhelp: {} failed to parse: {e}", path.display()),
         }
     }
+}
+
+/// Loads every `*.toml` file in the symptoms directory, keyed by file stem so
+/// a `SymptomOption::goto` of `"no-sound:check-mute"` can be resolved. Scans
+/// the system path (a pacman package's location) then the user content root
+/// (where bakery installs content — see `content::user_content_root`) —
+/// same "user copy wins on collision" precedent as `ContentStore::load`.
+pub fn load_all() -> std::collections::HashMap<String, Vec<SymptomNode>> {
+    let mut out = std::collections::HashMap::new();
+    scan_symptoms_dir(Path::new(SYSTEM_SYMPTOMS_DIR), &mut out);
+    scan_symptoms_dir(&super::user_content_root().join(SYMPTOMS_SUBPATH), &mut out);
     out
 }