docs(dotnet): document PostGuardConfig.HttpClient, Timeout, and IDisposable lifetime

[dobby-coder]

The E4A.PostGuard SDK gained two new PostGuardConfig properties in encryption4all/postguard-dotnet#19 that are not covered in docs/sdk/dotnet-encryption.md:

• HttpClient (HttpClient?, init-only). Optional caller-supplied client. When supplied, the SDK does NOT dispose it. Useful for DI scenarios.
• Timeout (TimeSpan?, init-only). Request timeout applied to the SDK-owned client. Ignored when HttpClient is supplied (caller owns the timeout in that case).

Also: PostGuard now implements IDisposable. When the SDK creates its own client (default), pg.Dispose() disposes it; an injected client is left alone.

The internal change is that PostGuard now reuses a single long-lived HttpClient built from a SocketsHttpHandler with PooledConnectionLifetime = 2min, fixing socket exhaustion under sustained load. Callers that previously created a new PostGuard per request should be told to reuse one instance.

What to update

docs/sdk/dotnet-encryption.md:

1. Add HttpClient and Timeout rows to the PostGuardConfig options table near the top of the file (right after Headers).
2. Add a short "Lifetime" subsection under "Constructor" explaining that PostGuard is IDisposable, owns its own HttpClient by default (which it disposes), and that callers can inject their own client via HttpClient = ... (the SDK won't dispose injected clients). Recommend reusing a single PostGuard per process for sustained workloads.
3. Mention that Timeout is ignored when an HttpClient is supplied.

Verify with npm run docs:build. Follow the style rules in postguard-docs/CLAUDE.md (no banned words, no em dashes, no bold inflation).

Source PR: encryption4all/postguard-dotnet#19

[dobby-coder]

/dobby

[dobby-coder]

Dobby is here, Dobby is here! Dobby will document the new HttpClient, Timeout, and IDisposable lifetime in docs/sdk/dotnet-encryption.md, build the site to verify, and open a draft PR. Dobby gets to work!

[dobby-coder]

Plan

File to edit: docs/sdk/dotnet-encryption.md

Changes:

1. Add two rows to the PostGuardConfig options table after Headers:
   • HttpClient — HttpClient?, optional. Caller-supplied client; not disposed by the SDK.
   • Timeout — TimeSpan?, optional. Applied to the SDK-owned client. Ignored when HttpClient is supplied.
2. Add a "Lifetime" subsection after the table explaining: PostGuard is IDisposable; by default it owns and disposes its own long-lived HttpClient; an injected client is left alone; reuse a single PostGuard per process for sustained workloads.
3. Cross-reference that Timeout is ignored when HttpClient is supplied (covered in both the table row and the prose).

Verification: npm run docs:build (baseline already green, 6.33s).

Style: No banned words, target zero em dashes / bold, plain direct voice per CLAUDE.md.

No code snippet — types are documented inline in the options table (consistent with existing rows for Headers, AllowInsecureUrls). No source-link needed.