Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/language_models/src/provider/bedrock.rs

@@ -365,10 +365,10 @@ struct BedrockModel {
 }
 
 impl BedrockModel {
-    fn get_or_init_client(&self, cx: &AsyncApp) -> Result<&BedrockClient, anyhow::Error> {
+    fn get_or_init_client(&self, cx: &AsyncApp) -> anyhow::Result<&BedrockClient> {
         self.client
             .get_or_try_init_blocking(|| {
-                let Ok((auth_method, credentials, endpoint, region, settings)) =
+                let (auth_method, credentials, endpoint, region, settings) =
                     cx.read_entity(&self.state, |state, _cx| {
                         let auth_method = state
                             .settings
@@ -390,10 +390,7 @@ impl BedrockModel {
                             region,
                             state.settings.clone(),
                         )
-                    })
-                else {
-                    return Err(anyhow!("App state dropped"));
-                };
+                    })?;
 
                 let mut config_builder = aws_config::defaults(BehaviorVersion::latest())
                     .stalled_stream_protection(StalledStreamProtectionConfig::disabled())
@@ -438,13 +435,11 @@ impl BedrockModel {
                 }
 
                 let config = self.handler.block_on(config_builder.load());
-                Ok(BedrockClient::new(&config))
+                anyhow::Ok(BedrockClient::new(&config))
             })
-            .map_err(|err| anyhow!("Failed to initialize Bedrock client: {err}"))?;
+            .context("initializing Bedrock client")?;
 
-        self.client
-            .get()
-            .ok_or_else(|| anyhow!("Bedrock client not initialized"))
+        self.client.get().context("Bedrock client not initialized")
     }
 
     fn stream_completion(
@@ -544,7 +539,10 @@ impl LanguageModel for BedrockModel {
 
             region
         }) else {
-            return async move { Err(anyhow!("App State Dropped")) }.boxed();
+            return async move {
+                anyhow::bail!("App State Dropped");
+            }
+            .boxed();
         };
 
         let model_id = match self.model.cross_region_inference_id(&region) {
@@ -720,7 +718,7 @@ pub fn into_bedrock(
             BedrockToolChoice::Any(BedrockAnyToolChoice::builder().build())
         }
         Some(LanguageModelToolChoice::None) => {
-            return Err(anyhow!("LanguageModelToolChoice::None is not supported"));
+            anyhow::bail!("LanguageModelToolChoice::None is not supported");
         }
     };
     let tool_config: BedrockToolConfig = BedrockToolConfig::builder()