fix(appkit): report only the actually-missing env vars in resource errors

[MarioCadenas]

Problem

ResourceRegistry.formatMissingResources (and the dev-mode warning banner) printed every field's env var for a missing resource via Object.values(entry.fields).map((f) => f.env) — regardless of whether that var was already set, and including env-less discovery-only fields (which map to undefined and render as stray empty entries).

For a multi-field resource like Lakebase Postgres, a single unset variable produced a confusing message listing all seven fields plus empty slots:

Missing required resources:
  - postgres:Postgres [lakebase] (set , , , PGHOST, PGDATABASE, LAKEBASE_ENDPOINT, PGPORT, PGSSLMODE)

…even when only PGPORT was actually missing. The real problem was buried.

Fix

Add a private unsetEnvVars() helper that returns only the env vars that are actually unset/empty, skipping fields that declare no env — mirroring the exact resolution check already in validate(). Both formatMissingResources and formatDevWarningBanner now use it, so the error lists exactly what the caller must set:

Missing required resources:
  - postgres:Postgres [lakebase] (set PGPORT)

Tests

• New: a partially-configured multi-field resource reports only the unset var, not the one already set.
• New: env-less discovery-only fields never appear (no stray empty entries).
• A mutation reverting the fix fails exactly these two tests.
• Full resource-registry suite: 26/26 pass; appkit typecheck + biome clean.

Scope

This is a reporting fix only. Separately, fields with a static "value" default in the manifest (e.g. PGPORT: "5432") are still reported as missing because validate() reads only process.env and ignores the "value" fallback — a deeper bug left out of this PR.

Branched from main; independent of the graceful-shutdown work in #441.

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📦 Bundle size report

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

@databricks/appkit

npm tarball (packed): 708 KB (+5.4 KB) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	732 KB (+3.9 KB)	256 KB (+1.3 KB)
Type declarations	276 KB (+1.9 KB)	94 KB (+642 B)
Source maps	1.4 MB (+12 KB)	478 KB (+3.9 KB)
Other	11 KB	3.7 KB
Total	2.4 MB (+17 KB)	832 KB (+5.9 KB)

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

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
.	79 KB (+148 B)	2.5 KB	81 KB (+148 B)	external	259 KB (+274 B)
./beta	39 KB (+457 B)	231 B (+1 B)	40 KB (+458 B)	external	118 KB (+1.2 KB)
./type-generator	19 KB	0 B	19 KB	external	54 KB

Chunks:

Entry	Chunk	Load	Size (gz)
.	index.js	initial	75 KB
.	utils.js	initial	4.0 KB
.	remote-tunnel-manager.js	lazy	2.5 KB
./beta	beta.js	initial	30 KB
./beta	databricks.js	initial	5.8 KB
./beta	service-context.js	initial	3.2 KB
./beta	client-options.js	initial	220 B
./beta	databricks.js	lazy	128 B
./beta	index.js	lazy	103 B
./type-generator	index.js	initial	19 KB

@databricks/appkit-ui

npm tarball (packed): 295 KB — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	350 KB	116 KB
Type declarations	201 KB	72 KB
Source maps	669 KB	218 KB
CSS	16 KB	3.3 KB
Total	1.2 MB	410 KB

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

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
./js	4.3 KB	49 KB	54 KB	208 KB	12 KB
./js/beta	20 B	0 B	20 B	0 B	0 B
./react	428 KB	49 KB	476 KB	1.3 MB	163 KB
./react/beta	20 B	0 B	20 B	0 B	0 B

Chunks:

Entry	Chunk	Load	Size (gz)
./js	index.js	initial	4.2 KB
./js	chunk	initial	120 B
./js	apache-arrow	lazy	49 KB
./js/beta	beta.js	initial	20 B
./react	index.js	initial	426 KB
./react	tslib	initial	2.1 KB
./react	apache-arrow	lazy	49 KB
./react/beta	beta.js	initial	20 B