fix(doctor): extract semver from opencode --version stdout

The Electron-based OpenCode build leaks log lines like
`00:24:25.202 > app starting { version: '1.14.33', packaged: true }`
into stdout, so `getOpenCodeVersion` was returning the entire log
line as the 'version'. `compareVersions` then split that string on
'.' and produced a nonsensical numeric array (e.g., `[0, 0, 14, 0]`),
which it judged as < the minimum 1.4.0. Result: doctor incorrectly
flagged OpenCode 1.14.x as below the minimum required version.

Replace the raw `stdout.trim()` return with a small
`extractSemverFromOutput` helper that runs a semver-shaped regex
across the output. A negative lookbehind `(?<![\d:])` skips the
milliseconds segment of timestamps (e.g., `25.202` in
`00:24:25.202`), so the parser locks onto the real version token.

Adds 12 unit tests covering plain semver, v-prefix, pre-release,
build metadata, the Electron regression, timestamp-only stdout,
and various invalid inputs.

Fixes #3765

src/cli/doctor/checks/system-binary.test.ts

@@ -0,0 +1,62 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, it } from "bun:test"
+import { extractSemverFromOutput } from "./system-binary"
+
+describe("extractSemverFromOutput", () => {
+  describe("#given clean version output #when extractSemverFromOutput #then returns the semver token", () => {
+    it("plain semver", () => {
+      expect(extractSemverFromOutput("1.14.33")).toBe("1.14.33")
+    })
+
+    it("v-prefixed semver strips the prefix", () => {
+      expect(extractSemverFromOutput("v1.14.33")).toBe("1.14.33")
+    })
+
+    it("trailing whitespace and newlines are tolerated", () => {
+      expect(extractSemverFromOutput("  1.14.33\n")).toBe("1.14.33")
+    })
+
+    it("pre-release suffix is preserved", () => {
+      expect(extractSemverFromOutput("1.0.0-beta.1")).toBe("1.0.0-beta.1")
+    })
+
+    it("build metadata is preserved", () => {
+      expect(extractSemverFromOutput("1.0.0+build.42")).toBe("1.0.0+build.42")
+    })
+  })
+
+  describe("#given Electron log-polluted stdout #when extractSemverFromOutput #then ignores the timestamp and finds the version", () => {
+    it("regression for #3765: Electron desktop dumps log lines into stdout", () => {
+      const polluted = "00:24:25.202 > app starting { version: '1.14.33', packaged: true }"
+      expect(extractSemverFromOutput(polluted)).toBe("1.14.33")
+    })
+
+    it("multi-line stdout with log prefix and trailing version", () => {
+      const polluted = "12:00:00.001 [info] starting opencode\n1.14.33\n"
+      expect(extractSemverFromOutput(polluted)).toBe("1.14.33")
+    })
+
+    it("timestamp-only stdout returns null", () => {
+      expect(extractSemverFromOutput("00:24:25.202 some log line")).toBe(null)
+    })
+  })
+
+  describe("#given empty or invalid output #when extractSemverFromOutput #then returns null", () => {
+    it("empty string", () => {
+      expect(extractSemverFromOutput("")).toBe(null)
+    })
+
+    it("only whitespace", () => {
+      expect(extractSemverFromOutput("   \n  ")).toBe(null)
+    })
+
+    it("text without any semver-shaped token", () => {
+      expect(extractSemverFromOutput("hello world")).toBe(null)
+    })
+
+    it("incomplete semver (only major.minor) is rejected", () => {
+      expect(extractSemverFromOutput("1.14")).toBe(null)
+    })
+  })
+})

src/cli/doctor/checks/system-binary.ts

@@ -105,6 +105,17 @@ export async function findOpenCodeBinary(): Promise<OpenCodeBinaryInfo | null> {
   return findDesktopBinary()
 }
 
+export function extractSemverFromOutput(output: string): string | null {
+  const trimmed = output.trim()
+  if (!trimmed) return null
+  // Match a semver-shaped token, allowing optional `v` prefix and `-prerelease+build` suffix.
+  // The negative lookbehind `(?<![\d:])` prevents matching the milliseconds segment of timestamps
+  // like `00:24:25.202` that the Electron-based OpenCode binary leaks into stdout.
+  const semverPattern = /(?<![\d:])v?(\d+\.\d+\.\d+(?:[-+][\w.]+)*)/
+  const match = trimmed.match(semverPattern)
+  return match?.[1] ?? null
+}
+
 export async function getOpenCodeVersion(
   binaryPath: string,
   platform: NodeJS.Platform = process.platform
@@ -113,7 +124,7 @@ export async function getOpenCodeVersion(
     const command = buildVersionCommand(binaryPath, platform)
     const result = await spawnWithTimeout(command, { stdout: "pipe", stderr: "pipe" })
     if (result.timedOut || result.exitCode !== 0) return null
-    return result.stdout.trim() || null
+    return extractSemverFromOutput(result.stdout)
   } catch {
     return null
   }