feat: drop @databricks/sdk-experimental from @databricks/lakebase

[MarioCadenas]

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

Changes

feat: drop @databricks/sdk-experimental from @databricks/lakebase

Lakebase now takes a structural workspace client: either the legacy
WorkspaceClient shape (currentUser.me + apiClient.request) or anything with an
authenticated request() (the AppKit modular client). Credential generation and
the SCIM Me lookup go through request() when present.

The default client (no workspaceClient passed) uses the modular sdk-core
profile resolution and sdk-auth default credentials, loaded via dynamic
import so the CJS build keeps working with the ESM-only SDK.

Token refresh timing and caching are unchanged.

feat(appkit): pass the modular workspace client to lakebase

The lakebase plugin and initializeLakebasePool hand the AppKit client to
@databricks/lakebase directly instead of toLegacyWorkspaceClient().

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 (+30 KB) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	1.3 MB (+28 KB)	458 KB (+11 KB)
Type declarations	463 KB (+7.8 KB)	168 KB (+2.9 KB)
Source maps	2.5 MB (+58 KB)	857 KB (+20 KB)
Other	11 KB	3.7 KB
Total	4.2 MB (+94 KB)	1.5 MB (+33 KB)

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

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
.	106 KB (+3.8 KB)	2.5 KB (+1 B)	108 KB (+3.8 KB)	external	343 KB (+11 KB)
./beta	102 KB (+3.7 KB)	486 B (+1 B)	103 KB (+3.7 KB)	external	307 KB (+9.8 KB)
./testing	45 KB (+3.2 KB)	32 KB (-2 B)	77 KB (+3.2 KB)	external	224 KB (+8.8 KB)
./tsdown	520 B	0 B	520 B	external	813 B
./type-generator	26 KB (+2.6 KB)	0 B	26 KB (+2.6 KB)	external	74 KB (+7.1 KB)

Chunks:

Entry	Chunk	Load	Size (gz)
.	index.js	initial	101 KB
.	utils.js	initial	4.6 KB
.	remote-tunnel-manager.js	lazy	2.5 KB
./beta	beta.js	initial	82 KB
./beta	stream-manager.js	initial	5.9 KB
./beta	modular.js	initial	5.8 KB
./beta	service-context.js	initial	4.2 KB
./beta	databricks.js	initial	3.3 KB
./beta	client.js	initial	653 B
./beta	index.js	initial	20 B
./beta	supervisor-api.js	lazy	192 B
./beta	databricks.js	lazy	179 B
./beta	index.js	lazy	115 B
./testing	manifest.js	initial	32 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	26 KB

@databricks/appkit-ui

npm tarball (packed): 397 KB (+579 B) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	429 KB (+235 B)	147 KB (+108 B)
Type declarations	267 KB (+887 B)	99 KB (+371 B)
Source maps	853 KB (+314 B)	286 KB (+143 B)
CSS	16 KB	3.2 KB
Total	1.5 MB (+1.4 KB)	534 KB (+622 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 (+12 B)	49 KB	481 KB (+12 B)	1.3 MB	177 KB (+41 B)
./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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📦 Try this PR's app template

Scaffolds a new app from this PR's SDK build. Run it in any folder (requires the GitHub CLI — gh auth login — and the Databricks CLI):

gh run download 38918707769 -R databricks/appkit -n appkit-template-0.88.1-pr.167ffac-feat-modular-lakebase-642 -D appkit-pr-642 \
  && unzip -o "appkit-pr-642/appkit-template-0.88.1-pr.167ffac-feat-modular-lakebase-642.zip" -d "appkit-pr-642" \
  && databricks apps init --template "appkit-pr-642"

The template pins @databricks/appkit and @databricks/appkit-ui to tarballs built from this branch, so the scaffolded app runs against this PR's code.