fix(ipc): keep the class-prefix strip case-sensitive

`stripErrorClassPrefix` took a case-insensitive flag from the two AccountsPane
copies it replaced, which widened `LinuxPackageInstallRecoveryCard` — that site
matched `/^Error:\s*/` on main. The only thing this trims is
`Error.prototype.toString()` output, which V8 always writes as `Error: `, so the
flag could never match a real class prefix the case-sensitive pattern misses; it
could only eat the lowercase severity marker git, rpm, dpkg and pip put in front
of a real reason. `IPC_ENVELOPE`'s own `\w*Error:` group in the same module is
already case-sensitive.

All three call sites now agree, and the card matches main again.

src/renderer/src/components/LinuxPackageInstallRecoveryCard.test.tsx

@@ -613,6 +613,27 @@ describe('LinuxPackageInstallRecoveryCard reveal', () => {
     // Why: a reveal failure is not a command-build failure, so the copy path must survive it.
     expect(button('Copy Install Command')).toBeTruthy()
   })
+
+  /**
+   * Why: package tooling writes its severity marker in lowercase — `error: Failed dependencies:`
+   * is rpm's own wording, not a stringified Error. Trimming it would leave the line reading as if
+   * the install had merely reported dependencies. This is the sensitivity this card had before the
+   * canonical stripper took the job over.
+   */
+  it('keeps a lowercase severity marker in the reason it shows', async () => {
+    showLinuxPackage.mockRejectedValue(
+      new Error(
+        "Error invoking remote method 'updater:showLinuxPackage': " +
+          'error: Failed dependencies: libc.so.6 is needed by orca-1.4.200'
+      )
+    )
+    renderCard()
+
+    fireEvent.click(button('Show Package'))
+    await flushActions()
+
+    expect(footnoteText()).toBe('error: Failed dependencies: libc.so.6 is needed by orca-1.4.200')
+  })
 })
 
 describe('LinuxPackageInstallRecoveryCard without a usable command', () => {

src/shared/ipc-invoke-envelope.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it } from 'vitest'
-import { stripIpcInvokeEnvelope, stripIpcInvokeEnvelopeFrom } from './ipc-invoke-envelope'
+import {
+  stripErrorClassPrefix,
+  stripIpcInvokeEnvelope,
+  stripIpcInvokeEnvelopeFrom
+} from './ipc-invoke-envelope'
 
 describe('stripIpcInvokeEnvelope', () => {
   it('returns the reason behind the invoke envelope', () => {
@@ -80,3 +84,33 @@ describe('stripIpcInvokeEnvelopeFrom', () => {
     expect(stripIpcInvokeEnvelopeFrom(null)).toBeNull()
   })
 })
+
+describe('stripErrorClassPrefix', () => {
+  it('removes the class prefix Error.prototype.toString() writes', () => {
+    expect(stripErrorClassPrefix('Error: updater is not initialized')).toBe(
+      'updater is not initialized'
+    )
+  })
+
+  /**
+   * Why case-sensitive: the only thing this trims is `Error.prototype.toString()` output, and V8
+   * writes the constructor name, so the prefix is always exactly `Error: `. A lowercase `error: `
+   * is never that — it is the severity marker git, rpm, dpkg and pip put in front of a real
+   * reason, and eating it drops the word the user is reading the line for.
+   */
+  it('keeps a lowercase severity marker, which is a reason and not a class name', () => {
+    expect(
+      stripErrorClassPrefix("error: pathspec 'v2' did not match any file(s) known to git")
+    ).toBe("error: pathspec 'v2' did not match any file(s) known to git")
+    expect(stripErrorClassPrefix('ERROR: Could not install packages due to an OSError')).toBe(
+      'ERROR: Could not install packages due to an OSError'
+    )
+  })
+
+  it('leaves a message that carries no class prefix alone', () => {
+    expect(stripErrorClassPrefix('Access denied')).toBe('Access denied')
+    expect(stripErrorClassPrefix('Error 500: upstream unavailable')).toBe(
+      'Error 500: upstream unavailable'
+    )
+  })
+})

src/shared/ipc-invoke-envelope.ts

@@ -33,9 +33,14 @@ export function stripIpcInvokeEnvelope(message: string): string | null {
  * `Error.prototype.toString()` renders "Error: <message>", so a rejection that was stringified
  * rather than read through `.message` arrives with a class prefix that is not part of the reason.
  * Separate from the envelope: a message can carry this prefix without ever crossing IPC.
+ *
+ * Case-sensitive, like the class name inside `IPC_ENVELOPE` above: V8 writes the constructor
+ * name, so the prefix is always exactly `Error: `. A lowercase `error: ` is git's, rpm's and
+ * pip's severity marker in front of a real reason, and trimming it would drop the word the line
+ * is being read for.
  */
 export function stripErrorClassPrefix(text: string): string {
-  return text.replace(/^Error:[ \t]*/i, '')
+  return text.replace(/^Error:[ \t]*/, '')
 }
 
 /**