feat(owen-ext): Owen extension substrate — Owen.Build host + Owen.TypedBuilder (OX-01)

.github/workflows/ci.yml

@@ -3455,6 +3455,38 @@ jobs:
           path: ${{ runner.temp }}/benchmark-scorecard.json
           retention-days: 90
 
+  # OX-01 (docs/notes/owen-extension-alpha-preregistration.md): the Owen extension substrate,
+  # with Typed Builder as extension #1. The gate packs Owen.Build (the generic host, with this
+  # platform's natively built Rust core) and Owen.TypedBuilder, then proves in a project OUTSIDE
+  # the checkout, with no Python / cargo / rustc / owen on PATH, that one PackageReference gives
+  # the generated API, CS errors, and OWN findings from `dotnet build` with canonical MSBuild
+  # coordinates; it replays the whole TB-MVP corpus and acceptance through the package, adds a
+  # second (synthetic) extension, and mutates the installed packages (M1-M7). Both platforms:
+  # MSBuild's Exec, the packed core and the paths all differ between them.
+  owen-extension:
+    name: Owen extension substrate (Owen.Build + Owen.TypedBuilder, isolated consumer)
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
+        with:
+          python-version: "3.13"
+      - uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4
+        with:
+          dotnet-version: "8.0.x"
+      - uses: dtolnay/rust-toolchain@fa04a1451ff1842e2626ccb99004d0195b455a88 # master, 2026-07-10
+        with:
+          toolchain: stable
+      - name: The extension gate (pack, isolated consumer A-H, mutations M1-M7)
+        run: python scripts/owen_extension_gate.py
+
   # Alpha gate A (issue #202): the single delightful command, proven end-to-end
   # on a clean runner — install -> check -> findings. Packaging only, no
   # analysis-behaviour change: the underlying project stays OwnSharp.Cli

docs/notes/alpha-readiness.md

@@ -68,6 +68,39 @@ None of those is research; all are the difference between "interesting PoC" and
 standing between here and the day 1–30 milestone being *literally* copy-paste
 for a stranger.
 
+## Update 2026-10-03: the extension path (OX-01)
+
+**A second install path now exists beside A.** No `dotnet tool` and no command: a
+`PackageReference`.
+
+```
+dotnet add package Owen.TypedBuilder
+dotnet build
+```
+
+**What it does.**
+- The package depends on **`Owen.Build`**, the generic build host. `Owen.Build` carries the same program as `Owen.Cli` (`owen`), its bundled extractor, and the Rust core for `linux-x64` and `win-x64`.
+- On every build it runs Owen once for every active Owen extension.
+- Findings are ordinary MSBuild diagnostics, so `dotnet build`, CI logs and Visual Studio's Error List all show them. They are `warning` by default and `OwenSeverity=error` to fail the build.
+
+The machine needs no Python, no Rust toolchain, no global tool and no checkout. The isolated
+consumer gate proves it on Linux and Windows CI (`scripts/owen_extension_gate.py`).
+
+**Extension #1 is the Typed Builder:**
+- typed states and a typed builder generated from one annotated EF entity;
+- illegal transitions are compiler errors;
+- stale or copied states are `OWN` findings on build.
+
+The contract a second extension uses is in [`spec/OwenExtension.md`](../../spec/OwenExtension.md). See
+[`owen-extension-alpha-report.md`](owen-extension-alpha-report.md) for the evidence, and
+[`owen-extension-ide-feasibility.md`](owen-extension-ide-feasibility.md) for live IDE diagnostics:
+- E1 (one generic VSIX host) is the direction, not built here;
+- E2 (a native Roslyn analyzer) was rejected.
+
+**Still open.** Exactly the items that already gated A: nothing is published to nuget.org
+yet, and there is no license. `Owen.Build` and `Owen.TypedBuilder` are 0.1.0 candidates packed
+from source.
+
 ## The 20% rule (other stacks)
 
 Other stacks are **proof of portability, not a second product.** Sanctioned now:

docs/notes/owen-diagnostics-model.md

@@ -0,0 +1,56 @@
+# Owen diagnostics: the model already exists (OX-01, P8)
+
+**Question.** Is the renderer so tied to CLI strings that the extension substrate needs a new
+internal diagnostic model before `msbuild`, `github`, `sarif`, a future Visual Studio host or a
+future LSP can be served?
+
+**Answer: no.** The model exists, it is the authoritative core's, and every surface is
+already one function of it. OX-01 adds **no** diagnostic layer. It consumes the existing one.
+
+## The model
+
+`own_bridge::verdict::Finding` (Rust, authoritative since the P-022 Stage 3 cutover; the Python
+reference mirrors it field for field):
+
+| field | the brief's concept |
+|---|---|
+| `code` | code (`OWN001` …) |
+| `severity` (+ `advisory`) | severity. The host's `--severity` changes only how a finding is **shown**, never the verdict |
+| `message` | message |
+| `file`, `line`, `column` (optional) | file, start line, start column |
+| `related: Vec<Step>`, `flow: Vec<Step>` | related locations and the witness path |
+| `kind` (`[resource: …]`), `component`, `event`, `handler` | the resource the finding is about |
+| `ignore_reason` | suppression (`// own:ignore` …) |
+
+**Renderers,** each a pure function of a `Finding`:
+
+| function | output |
+|---|---|
+| `own_bridge::render_finding(f, "human" \| "github" \| "msbuild", severity)` | one line per surface |
+| `own_bridge::build_sarif` | a SARIF 2.1.0 log |
+
+`own-cli ownir --format {human,github,msbuild,sarif}` exposes all four. `BR-V9` pins the
+bytes, and the CLI ledgers pin both engines.
+
+## How OX-01 uses it
+
+The build host (`owen build-check`) asks the core for `--format msbuild` and passes the lines
+through. It changes exactly one thing: it makes the **origin path** absolute against the project
+directory, so Visual Studio's Error List never has to guess a base. No message, code or
+severity is re-rendered by the host.
+
+The host's own conditions are the `OWENB` codes (spec/OwenExtension.md §4):
+- a descriptor rejected;
+- no engine for the platform;
+- a refusal.
+
+They are rendered by the host in the same canonical MSBuild shape. They are host
+diagnostics, not analysis findings, and they never reuse an `OWN` code.
+
+## Gaps, recorded and not changed here
+
+- **No column on the `msbuild` line.** `render_msbuild` prints `file(line)` although `Finding` carries an optional `column`.
+  - **Effect:** the Error List navigates to the line, not the column.
+  - **Why not here:** changing the line is a change to the core's pinned bytes (BR-V9, the CLI ledgers), which is foundation work.
+- **The line and the wording of state-protocol findings.** A stale state token is reported at the region entry, and in the generic resource wording ("IDisposable local … disposed"). This is issue **#393**, unchanged here.
+- **For a future IDE host or LSP:** both consume the same `Finding`. `--format sarif` already carries everything they need: code, level, message, region, related locations, code flows. A future `Owen.VisualStudio` or language server should read SARIF, or a structured JSON of the same `Finding`, from the one core, and never re-derive a finding.