docs: add Canon architectural documentation and missing appsettings.json

Co-authored-by: efargas <9705611+efargas@users.noreply.github.com>
Agent-Logs-Url: https://github.com/efargas/S7-Tools/sessions/b897eb8e-f12d-4c9a-9480-1455d2d22710

Author: Copilot

docs/canon/ARCHITECTURE.md

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+---
+title: "Canon Index — Architectural Foundation Documents"
+version: "1.0.0"
+created: "2026-03-23"
+status: "canon"
+tags: ["canon", "index", "architecture"]
+---
+
+# S7Tools Architectural Canon — Index
+
+> The **Canon** is the prescriptive architectural foundation for S7Tools. These documents define
+> the laws that **must** be followed by all code in the system. They are not descriptions of how
+> code currently works, but **mandates** for how it must be written.
+>
+> Generated through a comprehensive source code audit on 2026-03-23.
+
+---
+
+## Universal Canon (All Projects)
+
+| Document | Description |
+|----------|-------------|
+| [ARCHITECTURE.md](./ARCHITECTURE.md) | **The Constitution** — Core philosophy, hexagonal architecture, SOLID principles, 10 commandments, mandatory patterns, anti-patterns |
+| [DATA_FLOW.md](./DATA_FLOW.md) | **The Blueprint** — Unidirectional data flow diagrams: UI→ViewModel→Service→Domain→Infrastructure, configuration flow, logging flow, profile CRUD flow |
+| [STATE_MANAGEMENT.md](./STATE_MANAGEMENT.md) | **The Ledger Rules** — State taxonomy, ownership rules, ViewModel reactive patterns, settings/profile/job/connection/log state lifecycle |
+| [CORE_API_CONTRACT.md](./CORE_API_CONTRACT.md) | **The Engine Manual** — Formal internal API: `IApplicationSettingsService`, `IProfileManager<T>`, `IJobScheduler`, `IBootloaderService`, `ILogDataStore`, all hardware interfaces |
+
+---
+
+## System Blueprints (Project-Specific)
+
+| Document | Process | Complexity |
+|----------|---------|-----------|
+| [PLC_MEMORY_DUMP_PIPELINE.md](./PLC_MEMORY_DUMP_PIPELINE.md) | 14-stage PLC memory extraction workflow | Critical |
+| [JOB_EXECUTION_PIPELINE.md](./JOB_EXECUTION_PIPELINE.md) | Job lifecycle: enqueue → resource coordination → parallel execution → persistence | Critical |
+| [CONFIGURATION_AND_LOGGING_SYSTEM.md](./CONFIGURATION_AND_LOGGING_SYSTEM.md) | Complete appsettings schema, loading pipeline, logging architecture, anti-patterns audit | Critical |
+
+---
+
+## Audit Summary
+
+### Audit Date
+2026-03-23
+
+### Scope
+414 C# source files across 4 projects:
+- `S7Tools` (UI + Application Services)
+- `S7Tools.Core` (Domain)
+- `S7Tools.Infrastructure.Logging` (Logging Infrastructure)
+- `S7Tools.Diagnostics` (Dev Tooling)
+
+### Key Findings
+
+**Architecture Compliance**: ✅ High
+- Clean separation of Domain / Infrastructure / Presentation layers
+- All service interfaces defined in `S7Tools.Core`
+- No UI framework references in Core or Infrastructure
+
+**Configuration**: ✅ Compliant
+- Strongly-typed `AppSettings` with `[Range]`/`[Required]` validation
+- `WritableOptions<T>` pattern for atomic persistence
+- `IApplicationSettingsService` as single point of access
+- `ValidateOnStart()` prevents startup with invalid config
+
+**Logging**: ✅ Compliant
+- Custom `DataStoreLoggerProvider` (in-memory UI viewer)
+- `UnifiedLoggerProvider` + `FileLogSink` (persistent file output)
+- Per-task isolated log stores via `ITaskLoggerFactory`
+- Structured log templates used throughout
+
+**Active Refactoring in Progress**:
+- Phase 1 (SerialPort): ✅ Complete — decomposed into 3 specialized services + facade
+- Phase 2 (Socat): 🔄 In Progress — 4 specialized services + facade registered
+
+**No Legacy Code Found**:
+- Zero `TODO`, `FIXME`, `HACK`, `DEPRECATED` markers
+- No orphaned interfaces or dead code paths
+- No `Console.WriteLine` in service code (only in `--diag` path of `Program.cs`)
+- No string interpolation in log messages
+
+### Recommendations Encoded in Canon
+
+1. **Ensure `appsettings.json` is present** in repository root (`/src/S7Tools/`) as a build artifact.
+   Without it, application starts with all C# defaults (no error), which may not reflect intended production settings.
+
+2. **Add CI architecture test** to enforce that `S7Tools.Core` has zero `ProjectReference` to other S7Tools projects.
+
+3. **Complete Phase 2 Socat refactoring**: Remove legacy `SocatService` monolithic entry path after `SocatFacadeService` is fully validated.
+
+4. **Standardize log level for business events**: Ensure all "job started/completed" type messages use `Information`, not `Debug`.