feat(shared): add a modular auth + raw-request seam to the workspace client

[MarioCadenas]

Part of the migration off @databricks/sdk-experimental onto the modular @databricks/sdk-* SDK (see #562). Base: analytics-migration-sdk.

Changes

feat(shared): add a modular auth + raw-request seam to the workspace client

Add getHost(), authenticate(headers) and request(req) to the WorkspaceClient
facade, built only from mapToClientOptions and resolved the same way the
modular SDK's resolveClientConfig does (profile resolve + defaultCredentials).
request() sends through the modular transport, so it carries the AppKit
User-Agent, returns the raw Response, and throws the wrapper ApiError on
non-2xx.

Migrate the drop-in callers off the legacy config/apiClient: SCIM workspace
id probe, dev warehouse discovery (still skip_cannot_use=true), internal
telemetry, files upload, mlflow eval auth, and agents hosted-tool auth.

Also cache env-M2M OAuth tokens until 40s before expiry. sdk-auth 0.51.0's
newM2mCredentials mints a new token per request, unlike the legacy SDK; this
affected the already-migrated warehouses/statementExecution clients too.

Draft: implemented by an agent; needs review and a deployed SP + OBO check before it's marked ready.

This pull request and its description were written by Isaac.

[github-actions]

📦 Bundle size report

Compared against bundle-size-baseline.json (main).

@databricks/appkit

npm tarball (packed): 1.2 MB (+12 KB) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	1.2 MB (+11 KB)	451 KB (+4.4 KB)
Type declarations	459 KB (+3.2 KB)	167 KB (+1.3 KB)
Source maps	2.5 MB (+22 KB)	845 KB (+8.0 KB)
Other	11 KB	3.7 KB
Total	4.2 MB (+36 KB)	1.4 MB (+14 KB)

Per-entry composition (own code — deps external (as shipped))

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
.	103 KB (+1.0 KB)	2.5 KB (+1 B)	106 KB (+1.0 KB)	external	334 KB (+2.6 KB)
./beta	99 KB (+988 B)	484 B	100 KB (+988 B)	external	300 KB (+2.5 KB)
./testing	43 KB (+1.1 KB)	32 KB (+1 B)	75 KB (+1.1 KB)	external	218 KB (+3.0 KB)
./tsdown	520 B	0 B	520 B	external	813 B
./type-generator	24 KB (+1.0 KB)	0 B	24 KB (+1.0 KB)	external	69 KB (+2.8 KB)

Chunks:

Entry	Chunk	Load	Size (gz)
.	index.js	initial	98 KB
.	utils.js	initial	4.6 KB
.	remote-tunnel-manager.js	lazy	2.5 KB
./beta	beta.js	initial	81 KB
./beta	stream-manager.js	initial	5.9 KB
./beta	modular.js	initial	4.3 KB
./beta	service-context.js	initial	4.2 KB
./beta	databricks.js	initial	3.3 KB
./beta	client.js	initial	593 B
./beta	index.js	initial	20 B
./beta	supervisor-api.js	lazy	193 B
./beta	databricks.js	lazy	176 B
./beta	index.js	lazy	115 B
./testing	manifest.js	initial	30 KB
./testing	index.js	initial	10 KB
./testing	wide-event-emitter.js	initial	2.9 KB
./testing	index.js	lazy	28 KB
./testing	remote-tunnel-manager.js	lazy	2.5 KB
./testing	utils.js	lazy	1.8 KB
./tsdown	index.js	initial	520 B
./type-generator	index.js	initial	24 KB

@databricks/appkit-ui

npm tarball (packed): 397 KB (+102 B) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	428 KB	146 KB
Type declarations	266 KB (+191 B)	98 KB (+123 B)
Source maps	852 KB	285 KB
CSS	16 KB	3.2 KB
Total	1.5 MB (+191 B)	533 KB (+123 B)

Per-entry composition (consumer bundle — deps bundled, peerDeps external)

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
./js	5.3 KB	49 KB	55 KB	208 KB	14 KB
./js/beta	2.1 KB	0 B	2.1 KB	0 B	5.0 KB
./react	433 KB	49 KB	481 KB	1.3 MB	177 KB
./react/beta	4.9 KB	0 B	4.9 KB	0 B	12 KB

Chunks:

Entry	Chunk	Load	Size (gz)
./js	index.js	initial	5.2 KB
./js	chunk	initial	120 B
./js	apache-arrow	lazy	49 KB
./js/beta	beta.js	initial	2.1 KB
./react	index.js	initial	431 KB
./react	tslib	initial	2.1 KB
./react	apache-arrow	lazy	49 KB
./react/beta	beta.js	initial	4.9 KB

[github-actions]

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gh run download 37794004346 -R databricks/appkit -n appkit-template-0.87.0-pr.a8e9b83-feat-modular-auth-seam-644 -D appkit-pr-644 \
  && unzip -o "appkit-pr-644/appkit-template-0.87.0-pr.a8e9b83-feat-modular-auth-seam-644.zip" -d "appkit-pr-644" \
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