feat: ambient per-call options (the caller-side half of IpcContext)

[eduard-dumitru]

Follow-up to #127. That PR gave the receiver a way to reach the peer without a Message parameter (IpcContext.Current), so a contracts assembly need not reference UiPath.Ipc. The caller side had no equivalent: the only way to set a per-call deadline is to pass a Message argument — which puts the transport type back into the signature and costs a wire slot.

This adds the missing half.

using (IpcCallOptions.With(TimeSpan.FromSeconds(30)))
    await proxy.SendLogBatch(jobId, logs);      // POCO contract, no Message

with call_options(request_timeout=30):
    await proxy.SendLogBatch(job_id, batch)

Precedence

client default → ambient → explicit Message argument (still wins).

The wire is unchanged

Request.TimeoutInSeconds already carries the value and peers already honour it (Request.GetTimeout). This is purely a client-API addition — no protocol change, no version boundary between peers, only a package bump.

Why now

uipath-python streams job logs to the handler over a shared contract. Bounding those sends currently requires a trailing Message, which forced UiPath.Ipc into GenericExecutors.Contracts — exactly the dependency #127 existed to avoid.

Tests

• .NET: 5 new (nesting, restore-on-throw, flow isolation, and a real round trip proving a POCO contract call is bounded — and that the same call is unbounded without the scope). Full suite green: 103 net6.0 / 101 net461.
• Python: 8 new (contextvar semantics + wire-level assertions that TimeoutInSeconds carries the ambient, and that an explicit Message overrides it). Full client suite: 107 passed.
• Both wirings mutation-checked: disabling the ambient fails exactly the new round-trip/wire test and nothing else.

---

TypeScript — now included, Node only

Added in a second commit. Same shape as the other two halves:

withRequestTimeout(TimeSpan.fromSeconds(30), async () => {
    await proxy.SendLogBatch(jobId, logs);   // POCO contract, no Message
});

Deliberately Node-only. Tracking "the current asynchronous flow" needs AsyncLocalStorage, and browsers have no equivalent. So:

• callOptions / withRequestTimeout are exported from the node entry point only — importing them from the web build is a compile error, not a silent no-op.
• The read side (AmbientCallOptions) has to live in std, because RpcRequestFactory is shared code and cannot import from a platform entry point. It is a one-function seam with a comment saying so; with no provider installed it returns undefined and the web build behaves exactly as before. Both tsconfig.node.json and tsconfig.web.json typecheck clean.

We have no web end-users today, so the asymmetry costs nothing; if that ever changes, the seam is the place to add a browser implementation (TC39 AsyncContext, when it lands).

Verification: the new spec (test/node/core/CallOptions.test.ts) passes — 5 of 5 — and is mutation-checked: making AmbientCallOptions.current() always return undefined fails 3 of them.

It has to be run with the spec list narrowed, though, because the jasmine suite does not compile on master, independent of this PR:

test/std/bcl/AggregateDisposable.test.ts(73,63): error TS2345: 'number | boolean | Mock | {}' is not assignable to 'IDisposable'
test/std/bcl/AggregateDisposable.test.ts(153,34): error TS7006: Parameter 'x' implicitly has an 'any' type

Reproduced on a pristine origin/master worktree after a clean npm ci — same two errors, same lines. tsconfig.jasmine.json sets no include, so it compiles test/ as well, which tsconfig.node.json never does; that is why the build is green while the test run is not. Not fixed here — flagging it as a separate problem worth its own ticket.