Auto: focas-f4b — cnc_wrmacro + cnc_wrparam writes

Closes #269

docs/v2/implementation/focas-simulator-plan.md

@@ -29,6 +29,8 @@ command ids (and their request/response payloads) don't drift between the
 | `0x0010` | `pmc_rdpmcrng` | reads PMC byte ranges |
 | `0x0020` | `cnc_modal` | reads cached modal MSTB per profile |
 | ... | ... | ... |
+| **`0x0102`** | **`cnc_wrparam`** | **mutates per-profile parameter map; returns `EW_PASSWD` (`11`) when the profile's `unlock_state` is off (sets up F4-d's unlock workflow) — issue #269, plan PR F4-b** |
+| **`0x0103`** | **`cnc_wrmacro`** | **mutates per-profile macro map; integer-only writes for now (decimalPointCount=0) — issue #269, plan PR F4-b** |
 | **`0x0F1A`** | **`cnc_rdalmhistry`** | **dumps the per-profile alarm-history ring buffer (issue #267, plan PR F3-a)** |
 
 ## `cnc_rdalmhistry` mock behaviour
@@ -100,3 +102,94 @@ Integration test `Series/AlarmHistoryProjectionTests.cs` will assert:
 These tests are blocked on the focas-mock + integration-test project
 landing; the unit-test coverage in `FocasAlarmProjectionTests` already
 exercises every same-process invariant.
+
+## `cnc_wrparam` / `cnc_wrmacro` mock behaviour — issue #269, plan PR F4-b
+
+When the focas-mock fixture lands, it MUST implement the contract below.
+The .NET side already ships against this contract (`FwlibFocasClient.cs`
+write helpers, `FakeFocasClient` round-trip support); writing the simulator
+to the same shape lets the existing integration-test scaffolds at
+`tests/.../IntegrationTests/Series/ParameterWriteTests.cs` and
+`MacroWriteTests.cs` (when they materialise) light up without driver
+changes.
+
+### Per-profile state
+
+Each profile owns:
+
+- `parameters: Dict[int, int]` — map from parameter number to current value.
+- `macros: Dict[int, int]` — map from macro number to current scaled-int
+  value (decimal-point count fixed at 0 for F4-b).
+- `unlock_state: bool` — defaults `False`. When `False`, every
+  `cnc_wrparam` returns `EW_PASSWD` (numeric `11`) regardless of
+  parameter. Macro writes are NOT gated by `unlock_state`.
+- `last_write: Optional[LastWrite]` — most-recent successful
+  `(kind, number, value, ts)` tuple, surfaced via the admin endpoint
+  below for audit-log assertions.
+
+### `cnc_wrparam` request decode
+
+```
+[int16 LE datano][int16 LE axis][int8|int16|int32 LE value]
+```
+
+Width of the value field is determined by the request frame trailer
+length per the table in
+[`focas-wire-protocol.md`](./focas-wire-protocol.md). On
+`unlock_state == False` short-circuit to `[int16 LE 11]` (`EW_PASSWD`).
+Otherwise mutate `parameters[datano] = value`, set `last_write`, return
+`[int16 LE 0]`.
+
+### `cnc_wrmacro` request decode
+
+```
+[int16 LE number][int16 LE length=8][int32 LE mcr_val][int16 LE dec_val]
+```
+
+Always accept (no `unlock_state` gate). Mutate
+`macros[number] = mcr_val` (we ignore `dec_val` for F4-b — integer-only).
+Return `[int16 LE 0]`. Round-trip: a subsequent `cnc_rdmacro(number)`
+returns `(mcr_val, 0)`.
+
+### Admin endpoint — `POST /admin/mock_set_unlock_state`
+
+Toggles `unlock_state` for the F4-d unlock workflow tests. Without this,
+F4-b parameter-write integration tests can't reproduce the
+`EW_PASSWD` → `BadUserAccessDenied` mapping.
+
+```
+POST /admin/mock_set_unlock_state
+{ "profile": "Series30i", "unlocked": true }
+```
+
+### Admin endpoint — `GET /admin/mock_get_last_write`
+
+Returns the simulator's view of the most-recent successful write, used by
+F4-b audit-log integration assertions ("did the write actually reach the
+fixture, and is the audit log capturing the right kind/number/value?").
+
+```
+GET /admin/mock_get_last_write?profile=Series30i
+->
+{
+  "kind": "param",            // "param" | "macro"
+  "number": 1815,
+  "value": 100,
+  "writtenAt": "2026-04-25T13:30:00Z"
+}
+```
+
+When no write has happened the endpoint returns `null` rather than 404 so
+the test helper can assert "no writes since fixture reset" without
+exception handling.
+
+### Status
+
+focas-mock simulator has not landed yet (tracked separately from F4-b).
+F4-b lands the .NET-side wire encoders + dispatch + status mapping
+unconditionally; the integration-test scaffolds at
+`tests/.../IntegrationTests/Series/ParameterWriteTests.cs` and
+`MacroWriteTests.cs` are deferred until the simulator + integration-test
+project land. Until then unit-test coverage in
+`FocasWriteParameterTests` / `FocasWriteMacroTests` exercises every
+same-process invariant against the in-memory `FakeFocasClient`.