refactor: replace empty catch blocks with descriptive comments

Empty catch blocks silently swallow errors, making debugging harder and
violating code quality best practices. This adds explanatory comments
to all empty catch blocks in core.ts and cli.ts, and replaces the
abrupt process.exit(1) in readScriptFromHttp with a proper Fail error
for consistent error handling.

Ref #1394

Author: apoorvdarshan

src/cli.ts

@@ -193,7 +193,9 @@ function linkNodeModules(cwd: string, external: string): string {
 function lstat(p: string) {
   try {
     return fs.lstatSync(p)
-  } catch {}
+  } catch {
+    // File does not exist — return undefined.
+  }
 }
 
 async function readScript() {
@@ -247,7 +249,8 @@ async function readScriptFromHttp(remote: string): Promise<string> {
   const res = await fetch(remote)
   if (!res.ok) {
     console.error(`Error: Can't get ${remote}`)
-    process.exit(1)
+    process.exitCode = 1
+    throw new Fail(`Failed to fetch remote script: ${remote} (${res.status})`)
   }
   return res.text()
 }

src/core.ts

@@ -1005,7 +1005,9 @@ try {
   if (isString(shell)) $.shell = shell
   if (isString(prefix)) $.prefix = prefix
   if (isString(postfix)) $.postfix = postfix
-} catch (err) {}
+} catch (err) {
+  // Bash may not be available (e.g. on Windows). Fall back to the default shell.
+}
 
 let cwdSyncHook: AsyncHook
 
@@ -1056,17 +1058,25 @@ export async function kill(
   )
     return
 
+  // Kill all child processes in the tree. Errors are expected here since
+  // processes may have already exited by the time we attempt to kill them.
   for (const p of await ps.tree({ pid, recursive: true })) {
     try {
       process.kill(+p.pid, signal)
-    } catch (e) {}
+    } catch (e) {
+      // Process already exited.
+    }
   }
   try {
+    // Try killing the process group first (negative pid).
     process.kill(-pid, signal)
   } catch (e) {
     try {
+      // If process group kill fails, try killing the process directly.
       process.kill(+pid, signal)
-    } catch (e) {}
+    } catch (e) {
+      // Process already exited.
+    }
   }
 }