Linter: Duration/Interval integer properties must include a unit suffix

Parent: #4442

## Convention

**DO** End property or parameter names of type integer that represent intervals or durations with units, e.g. `MonitoringInterval` → `MonitoringIntervalInSeconds`. If value is not ISO 8601 duration/time, drop `Interval`/`Duration` suffix and use unit.

> Source: [Azure SDK for .NET Mgmt Naming Conventions](https://github.com/Azure/azure-sdk-for-net/blob/main/doc/dev/Mgmt-Naming-Conventions.md)

## Observed today

A scan of `Azure/azure-rest-api-specs` (334 `client.tsp` files, 10,754 csharp-scoped `@@clientName` decorators) shows **79** decorators currently encoding this rule by hand. Examples:

- `diskSizeGB` → `DiskSizeInGB` (azurelargeinstance/resource-manager/Microsoft.AzureLargeInstance/AzureLargeInstance/client.tsp)
- `blockSizeBytes` → `BlockSizeInBytes` (azurestackhci/resource-manager/Microsoft.AzureStackHCI/StackHCIVM/client.tsp)
- `diskSizeGB` → `DiskSizeInGB` (azurestackhci/resource-manager/Microsoft.AzureStackHCI/StackHCIVM/client.tsp)
- `logicalSectorBytes` → `LogicalSectorInBytes` (azurestackhci/resource-manager/Microsoft.AzureStackHCI/StackHCIVM/client.tsp)
- `physicalSectorBytes` → `PhysicalSectorInBytes` (azurestackhci/resource-manager/Microsoft.AzureStackHCI/StackHCIVM/client.tsp)
- `memoryMB` → `MemoryInMB` (azurestackhci/resource-manager/Microsoft.AzureStackHCI/StackHCIVM/client.tsp)

## Proposed linter

**Detection**

Flag integer-typed properties whose name ends with `Interval`, `Duration`, `Timeout`, `Period`, or contains `Size`/`Length` without an `In` suffix. Allowed units: `InSeconds`, `InMilliseconds`, `InMs`, `InMinutes`, `InHours`, `InDays`, `InBytes`, `InKB`, `InMB`, `InGB`, `InTB`.

**Auto-fix**

Suggest `In` rename via `@@clientName`. Unit must be supplied by author or inferred from `@encode("seconds", int32)` etc.

**Scope**

The rule should be csharp-scoped — it only flags violations of the .NET convention, not the underlying TypeSpec name. It should suggest inserting a `@@clientName(..., "csharp")` override when the underlying TypeSpec name is intentional, or renaming the TypeSpec model when the convention applies cross-language.

## Acceptance criteria

- [ ] New lint rule registered in the appropriate ruleset (`@azure-tools/typespec-client-generator-core` or `@azure-tools/typespec-azure-resource-manager`).
- [ ] Doc page under `website/src/content/docs/docs/libraries/.../rules/`.
- [ ] Unit tests covering positive / negative cases and the auto-fix.
- [ ] A `.chronus/changes/` entry.

Start by inspecting existing lint rules and registration in @azure-tools/typespec-client-generator-core and @azure-tools/typespec-azure-resource-manager. Then review the rule documentation layout under website/src/content/docs/docs/libraries/.../rules/ and existing unit tests and .chronus/changes/ entries. Done means the csharp-scoped rule, positive and negative tests, auto-fix coverage, documentation page, and change entry are present.

Written by the indexing model from the issue text.