add typed JSON parser for brew outdated

parseOutdatedJSON decodes brew outdated --json into OutdatedPackages,
which separates formulae from casks — the plain-text output is just
names with no type information. Codable structs mirror the JSON shape,
with convertFromSnakeCase mapping installed_versions to Swift naming.
Undecodable input (brew error text, empty output) parses as .none.

The legacy line parser stays until callers switch over next commit.
Covered by 4 new unit tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

BrewBar/BrewParser.swift

@@ -1,5 +1,36 @@
 import Foundation
 
+struct OutdatedPackage: Codable, Equatable {
+    let name: String
+    let installedVersions: [String]
+    let currentVersion: String
+
+    /// Menu label, e.g. "wget 1.21 → 1.22"
+    var label: String {
+        let installed = installedVersions.joined(separator: ", ")
+        return "\(name) \(installed) → \(currentVersion)"
+    }
+}
+
+struct OutdatedPackages: Codable, Equatable {
+    let formulae: [OutdatedPackage]
+    let casks: [OutdatedPackage]
+
+    var all: [OutdatedPackage] {
+        formulae + casks
+    }
+
+    var isEmpty: Bool {
+        formulae.isEmpty && casks.isEmpty
+    }
+
+    var count: Int {
+        formulae.count + casks.count
+    }
+
+    static let none = OutdatedPackages(formulae: [], casks: [])
+}
+
 enum BrewParser {
     static func parseOutdated(_ output: String) -> [String] {
         output.split(separator: "\n")
@@ -7,6 +38,21 @@ enum BrewParser {
             .filter { !$0.isEmpty }
     }
 
+    /// Parses `brew outdated --json` output. Returns .none for anything
+    /// undecodable (brew error text, empty output) — same effect as an
+    /// empty result, and the raw output is already in the log window.
+    static func parseOutdatedJSON(_ output: String) -> OutdatedPackages {
+        let decoder = JSONDecoder()
+        decoder.keyDecodingStrategy = .convertFromSnakeCase // installed_versions → installedVersions
+
+        guard let data = output.data(using: .utf8),
+              let parsed = try? decoder.decode(OutdatedPackages.self, from: data)
+        else {
+            return .none
+        }
+        return parsed
+    }
+
     static func parseVersion(_ output: String) -> String {
         output.split(separator: "\n").first.map(String.init) ?? "Unknown"
     }

BrewBarTests/BrewBarTests.swift

@@ -22,6 +22,56 @@ final class BrewParserTests: XCTestCase {
         XCTAssertEqual(BrewParser.parseOutdated(output), ["wget"])
     }
 
+    // MARK: - parseOutdatedJSON
+
+    func testParseOutdatedJSON_formulaeAndCasks() {
+        let output = """
+        {
+          "formulae": [
+            {
+              "name": "wget",
+              "installed_versions": ["1.21.3"],
+              "current_version": "1.21.4",
+              "pinned": false,
+              "pinned_version": null
+            }
+          ],
+          "casks": [
+            {
+              "name": "tailscale-app",
+              "installed_versions": ["1.98.5"],
+              "current_version": "1.98.8",
+              "pinned": false,
+              "pinned_version": null
+            }
+          ]
+        }
+        """
+
+        let result = BrewParser.parseOutdatedJSON(output)
+        XCTAssertEqual(result.formulae.map(\.name), ["wget"])
+        XCTAssertEqual(result.casks.map(\.name), ["tailscale-app"])
+        XCTAssertEqual(result.count, 2)
+        XCTAssertFalse(result.isEmpty)
+        XCTAssertEqual(result.all.map(\.name), ["wget", "tailscale-app"])
+    }
+
+    func testParseOutdatedJSON_nothingOutdated() {
+        let result = BrewParser.parseOutdatedJSON("{\"formulae\": [], \"casks\": []}")
+        XCTAssertTrue(result.isEmpty)
+        XCTAssertEqual(result.count, 0)
+    }
+
+    func testParseOutdatedJSON_invalidInputReturnsNone() {
+        XCTAssertEqual(BrewParser.parseOutdatedJSON(""), .none)
+        XCTAssertEqual(BrewParser.parseOutdatedJSON("Error: some brew failure"), .none)
+    }
+
+    func testParseOutdatedJSON_packageLabel() {
+        let package = OutdatedPackage(name: "wget", installedVersions: ["1.21.3"], currentVersion: "1.21.4")
+        XCTAssertEqual(package.label, "wget 1.21.3 → 1.21.4")
+    }
+
     // MARK: - parseVersion
 
     func testParseVersion_picksFirstLine() {