improvements: apply all 8 code quality & feature suggestions

[efekurucay]

Summary

This PR implements all 8 improvements identified during the code review of the RLeon repository. Each suggestion is addressed in a dedicated commit so the history is easy to bisect.

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Changes by suggestion

1 — Codable ToolDefinition struct (code quality)

New file: RLeon/Tools/ToolDefinitionModels.swift

• Introduces ToolDefinition, ToolFunction, ToolParameters, ToolProperty as Codable types.
• BuiltInToolDefinitions.all replaces the 120+ line [String: Any] literal block in OllamaToolCalling.
• Adding or removing a tool is now a single declarative entry; typos are caught at compile time.

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2 — Centralised AppSettings (architecture)

New file: RLeon/App/AppSettings.swift

• Single @MainActor ObservableObject that owns every UserDefaults key: ollamaBaseURL, ollamaModel, ollamaUseTools, rleonSystemPrompt, plus all ToolSafetySettings keys.
• Registers defaults inside init() — RLeonApp.onAppear no longer duplicates that call.
• AppState vends the instance; passed as @EnvironmentObject into ContentView.
• Magic string keys scattered across FnPushToTalkCoordinator and OllamaToolCalling are eliminated.

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3 — Injectable URLSession (testability)

Modified files: OllamaClient.swift, OllamaToolCalling.swift

• listModels, chat, and chatWithLocalTools accept an optional URLSession (default: .shared).
• Tests can pass a URLSession backed by a URLProtocol stub — no real Ollama server needed.
• Directly enables the "unit / integration tests" roadmap milestone.

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4 — Shell security: Process(/bin/zsh) replaces AppleScript do script (security)

Modified file: OllamaToolCalling.swift — runShellCommand()

• Removes the osascript do script "\(interpolation)" path entirely.
• Runs commands via /bin/zsh -c using Process(), captures stdout + stderr, returns output to the model (capped at 64 KiB).
• Eliminates the AppleScript string-interpolation injection surface; output is now visible to the model instead of silently discarded.

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5 — Streaming support (UX)

New file: RLeon/LLM/OllamaStreamClient.swift
Modified file: OllamaChatView.swift

• OllamaStreamClient.stream(...) returns an AsyncThrowingStream<String, Error> using URLSession.AsyncBytes + Ollama stream: true.
• OllamaChatView gains a "Stream tokens" toggle (@AppStorage ollamaUseStreaming, default true).
• When enabled, assistantReply grows token-by-token via @MainActor updates — no more blank window during long responses.
• Falls back to non-streaming path automatically when tool calling is active (multi-round loop requirement).

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6 — Configurable hotkey (UX)

New files: RLeon/System/HotkeySettings.swift, RLeon/UI/HotkeySettingsView.swift

• HotkeyBinding struct stores keyCode + NSEvent.ModifierFlags; defaults to Fn (keyCode 63).
• HotkeySettings.current reads/writes to UserDefaults; reset() restores the Fn default.
• HotkeySettingsView: three-state recording UI (idle → recording → pending(binding)), uses a global NSEvent monitor to capture the next key press.
• Surfaced in ContentView.settingsTab alongside existing sections.

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7 — MCP multi-server config + async transport scaffold (feature foundation)

Modified file: RLeon/Tools/MCPToolBridge.swift
New file: RLeon/UI/MCPSettingsView.swift

• MCPServerConfig (Codable) holds name / command / args / env / URL per server.
• MCPBridgeRegistry persists the server list to UserDefaults as JSON.
• MCPToolBridge.shared now exposes configuredServers, addServer(_:), removeServer(id:).
• executeIfNeeded returns a richer error including transport hint when a call arrives before swift-sdk is wired.
• Clear TODO comments mark the exact integration points for swift-sdk (tools/list, tools/call) once Xcode 16+ is adopted.
• MCPSettingsView: list servers, enable/disable toggle, trash button, "Add server" sheet.

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8 — CI hardening: SwiftLint + test step + Release build (CI/CD)

Modified file: .github/workflows/ci.yml
New file: .swiftlint.yml

• Adds a lint job using norio-nomura/action-swiftlint@3.2.1 (--strict mode).
• Adds a test job that runs xcodebuild test and passes gracefully when no test target exists yet (prints an informative message instead of failing).
• Adds a Release build step alongside the existing Debug step.
• Extends branch triggers to improvements/**, feature/**, fix/**.
• .swiftlint.yml configures sensible defaults: 140-char line length, opt-out of todo/fixme in CI, enable useful opt-in rules (sorted_imports, empty_count, etc.).

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Files changed

File	Change
RLeon/Tools/ToolDefinitionModels.swift	new — Codable tool schema types + BuiltInToolDefinitions
RLeon/App/AppSettings.swift	new — centralised UserDefaults wrapper
RLeon/LLM/OllamaStreamClient.swift	new — streaming client
RLeon/System/HotkeySettings.swift	new — hotkey persistence
RLeon/UI/HotkeySettingsView.swift	new — hotkey picker UI
RLeon/UI/MCPSettingsView.swift	new — MCP server management UI
RLeon/LLM/OllamaClient.swift	modified — injectable URLSession
RLeon/LLM/OllamaToolCalling.swift	modified — typed defs, injectable session, Process shell
RLeon/LLM/OllamaChatView.swift	modified — streaming toggle + live token display
RLeon/Tools/MCPToolBridge.swift	modified — multi-server config, TODO transport scaffold
RLeon/App/AppState.swift	modified — vends AppSettings
RLeon/App/RLeonApp.swift	modified — passes AppSettings as EnvironmentObject
RLeon/UI/ContentView.swift	modified — surfaces new Settings sections
.github/workflows/ci.yml	modified — SwiftLint + test + Release build
.swiftlint.yml	new — linting configuration

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Testing checklist

• Build succeeds (Debug + Release) on macOS 14+
• Tool definitions compile correctly from BuiltInToolDefinitions.all
• Ollama chat works with streaming toggle on and off
• run_terminal_command runs via /bin/zsh, stdout is returned to the model
• Hotkey recorder captures a binding, saves, and app restarts with new binding
• MCP Settings section: add/remove server, enable/disable persists
• AppSettings values survive app restart (UserDefaults round-trip)
• SwiftLint CI step passes

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All changes are backward-compatible. No existing UserDefaults keys were renamed; migration paths are preserved.