* feat: screenshot digest response-view — Phase 4

Add a `screenshot` entry to the Phase 4 RESPONSE_VIEWS registry. At
responseLevel `digest`, the view keeps the cheap result fields — the
captured `path` and the `artifacts` retrieval handle — and collapses the
token-heavy `overlayRefs` array (each carrying ref + label + three
geometry rects) to a total `overlayCount` plus the first 12 refs leveled
down to `{ ref, label }`. `default`/`full` return today's shape unchanged,
so unregistered and default-level responses stay byte-identical.

* fix: preserve the screenshot digest through the client capture path

The daemon screenshot view returns a leveled digest (path, overlayCount, leveled
overlayRefs, artifacts), but client.capture.screenshot() always ran the data
through readScreenshotResultData, which keeps only path + full-geometry overlay
refs and drops overlayCount/artifacts — so the digest never reached SDK/CLI
callers. Make the capture method level-aware: when the effective responseLevel
(request override or client config) is non-default, return the leveled payload
verbatim instead of normalizing it. Default-level behavior is unchanged.

Adds shipped-path client tests: capture.screenshot({ responseLevel: 'digest' })
returns the raw digest (overlayCount/artifacts preserved, no normalizer
identifiers); the default path still normalizes. Kept the return type as
CaptureScreenshotResult (the union variant cascaded into many default-path
consumers); the caller opted into the level, so the runtime value is leveled.

* fix: preserve the screenshot digest through the CLI command path

agent-device screenshot --level digest --json still dropped overlayCount and
artifacts: the CLI command rebuilt the default { path, overlayRefs } shape from
the (now leveled) client result. Make screenshotCommand level-aware — for a
non-default responseLevel it emits the leveled payload verbatim (JSON / JSON
text). Adds a CLI shipped-path test (--level digest --json preserves the digest;
the default level still emits the normalized shape). Factors the predicate into
a shared isNonDefaultResponseLevel in contracts.ts, reused by the client helper.

* fix: preserve snapshot digest through the client capture path — Phase 4 (#949)

* fix: preserve the snapshot digest through the client capture path

client.capture.snapshot() always ran the daemon data through
normalizeSnapshotResult, which expects the full `nodes` tree — so a non-default
responseLevel digest ({ nodeCount, refs }) collapsed to an empty snapshot, the
same gap #945 fixed for screenshot. Make it level-aware: when the effective
responseLevel is non-default, return the leveled payload verbatim. Default-level
behavior is unchanged. Adds a shipped-path client test asserting the digest
survives (nodeCount/refs preserved, no normalizer identifiers).

* fix: preserve leveled digests through the generic CLI path

agent-device snapshot --level digest --json dropped nodeCount/refs: snapshot
goes through the generic CLI path (runCliCommandWithOutput -> formatCliOutput),
whose snapshot formatter serializes the default CaptureSnapshotResult shape and
discards digest-only fields. Make runGenericClientBackedCommand level-aware: for
a non-default responseLevel it emits the raw leveled payload verbatim (JSON /
JSON text), bypassing the default-shape formatter. This generalizes to any
generic-path command. Adds a snapshot CLI shipped-path test.