fix(platform): surface Nix-managed agent CLI install paths

The packaged macOS (and Linux) Desktop app did not discover agent
CLIs installed through nix-darwin `environment.systemPackages` or
per-user `nix profile install`. After launching from Finder and
rescanning, Codex / Claude Code / Gemini resolved cleanly from a
terminal but were reported as not found on `PATH`.

Root cause: in a GUI-launched Electron process the inherited `PATH`
is minimal (launchd does not source the user's shell rc), so
discovery relies on `wellKnownUserToolchainBins` in
`packages/platform/src/toolchain.ts`. The helper's well-known
list covered Homebrew, npm/nvm/fnm/mise/asdf, Deno, Go, pyenv,
Scoop, Volta, Vite+, Kimi, Bun, Cargo and the system Homebrew
locations, but did not include the standard Nix install roots:

- `/run/current-system/sw/bin` (NixOS / nix-darwin system profile)
- `~/.nix-profile/bin` (per-user Nix profile)

Both are documented well-known paths in Nix documentation and are
the canonical locations CLIs installed via `environment.systemPackages`
or `nix profile install` end up in.

Changes:

- `packages/platform/src/toolchain.ts`:
  - Add `~/.nix-profile/bin` to the user-level CLI install list
    (alongside Deno / Go / pyenv) so single-user Nix installs are
    surfaced the same way Homebrew/etc are. Best-effort — a missing
    dir contributes nothing; the existing `<dir>/bin` join behaviour
    is preserved.
  - Add `/run/current-system/sw/bin` to the
    `includeSystemBins`-gated block, next to `/opt/homebrew/bin`
    and `/usr/local/bin`. Same rationale: a NixOS / nix-darwin
    system-installed CLI lives here, and a GUI-launched daemon
    needs the explicit probe to find it.

- `packages/platform/tests/index.test.ts`:
  - Extend the existing "Deno, Go, pyenv" user-level test to also
    assert `~/.nix-profile/bin` is returned.
  - Extend both `includeSystemBins` true/false tests to also
    assert `/run/current-system/sw/bin` is included / omitted
    accordingly. Two assertions in two existing tests, no new
    test cases to keep the file dense.

Verified: `pnpm --filter @open-design/platform test` passes 76/76
tests, `pnpm --filter @open-design/platform typecheck` clean.

Fixes #6121

Signed-off-by: xxiaoxiong <2482929840@qq.com>

Author: xxiaoxiong

packages/platform/src/toolchain.ts

@@ -135,11 +135,15 @@ export function wellKnownUserToolchainBins(
     join(home, ".npm-packages", "bin"),
     // Other common user-level toolchains that install CLI shims outside the
     // Node ecosystem but still ship agent CLIs (or their dependencies):
-    // Deno's install root, Go's default GOBIN, and pyenv's shim dir. All are
-    // best-effort — a missing dir contributes nothing.
+    // Deno's install root, Go's default GOBIN, pyenv's shim dir, and the
+    // per-user Nix profile. All are best-effort — a missing dir contributes
+    // nothing. The Nix profile covers `nix profile install`'d CLIs for hosts
+    // (single-user installs or HOME-managed profiles) without
+    // /run/current-system/sw/bin.
     join(home, ".deno", "bin"),
     join(home, "go", "bin"),
     join(home, ".pyenv", "shims"),
+    join(home, ".nix-profile", "bin"),
   );
 
   // Windows-only user install roots that GUI launches miss. Scoop drops
@@ -167,7 +171,15 @@ export function wellKnownUserToolchainBins(
   }
 
   if (includeSystemBins) {
-    dirs.push("/opt/homebrew/bin", "/usr/local/bin");
+    dirs.push(
+      "/opt/homebrew/bin",
+      "/usr/local/bin",
+      // NixOS and nix-darwin expose system-installed CLIs here.
+      // GUI-launched daemons inherit a minimal PATH that omits
+      // this path even though user-installed agent CLIs (codex,
+      // claude, gemini, …) live here.
+      "/run/current-system/sw/bin",
+    );
   }
   // Per-version Node toolchains: scan the install root and surface every
   // version directory's bin folder. Best-effort — missing roots simply

packages/platform/tests/index.test.ts

@@ -805,15 +805,17 @@ describe("wellKnownUserToolchainBins", () => {
   });
 
   // Non-Node user toolchains that still ship agent CLIs (or their deps):
-  // Deno's install root, Go's default GOBIN, and pyenv's shim dir. GUI
-  // launches inherit a stripped PATH, so these must be searched explicitly.
-  it("includes Deno, Go, and pyenv user toolchain dirs", () => {
+  // Deno's install root, Go's default GOBIN, pyenv's shim dir, and the
+  // per-user Nix profile. GUI launches inherit a stripped PATH, so these
+  // must be searched explicitly.
+  it("includes Deno, Go, pyenv, and ~/.nix-profile/bin user toolchain dirs", () => {
     const home = mkdtempSync(join(tmpdir(), "wkutb-extra-"));
     try {
       const dirs = wellKnownUserToolchainBins({ home, env: {}, includeSystemBins: false });
       expect(dirs).toContain(join(home, ".deno", "bin"));
       expect(dirs).toContain(join(home, "go", "bin"));
       expect(dirs).toContain(join(home, ".pyenv", "shims"));
+      expect(dirs).toContain(join(home, ".nix-profile", "bin"));
     } finally {
       rmSync(home, { recursive: true, force: true });
     }
@@ -1112,23 +1114,25 @@ describe("wellKnownUserToolchainBins", () => {
     }
   });
 
-  it("includes /opt/homebrew/bin and /usr/local/bin when includeSystemBins is true", () => {
+  it("includes /opt/homebrew/bin and /usr/local/bin and /run/current-system/sw/bin when includeSystemBins is true", () => {
     const home = mkdtempSync(join(tmpdir(), "wkutb-sys-"));
     try {
       const dirs = wellKnownUserToolchainBins({ home, env: {}, includeSystemBins: true });
       expect(dirs).toContain("/opt/homebrew/bin");
       expect(dirs).toContain("/usr/local/bin");
+      expect(dirs).toContain("/run/current-system/sw/bin");
     } finally {
       rmSync(home, { recursive: true, force: true });
     }
   });
 
-  it("omits /opt/homebrew/bin and /usr/local/bin when includeSystemBins is false", () => {
+  it("omits /opt/homebrew/bin, /usr/local/bin, and /run/current-system/sw/bin when includeSystemBins is false", () => {
     const home = mkdtempSync(join(tmpdir(), "wkutb-nosys-"));
     try {
       const dirs = wellKnownUserToolchainBins({ home, env: {}, includeSystemBins: false });
       expect(dirs).not.toContain("/opt/homebrew/bin");
       expect(dirs).not.toContain("/usr/local/bin");
+      expect(dirs).not.toContain("/run/current-system/sw/bin");
     } finally {
       rmSync(home, { recursive: true, force: true });
     }