feat(build): compile with the TypeScript 7 native compiler

[raymondfeng]

Upgrades the monorepo to TypeScript 7, using the side-by-side install recommended
for TypeScript 7:

"@typescript/native": "npm:typescript@~7.0.2",
"typescript": "npm:@typescript/typescript6@~6.0.2"

TypeScript 7 no longer ships the JS compiler API — its exports["."] resolves to
lib/version.cjs — so anything that introspects the compiler (@typescript-eslint,
editor language services, tsserver) needs the API that @typescript/typescript6
still provides. The two packages declare different bin names (tsc vs tsc6), so
they coexist with no collision.

packages/build/package.json is the source of truth; bin/sync-dev-deps propagates
the spec to every workspace package, and bin/update-template-deps carries it into
the lb4 scaffolding templates. lb-tsc prefers the native compiler and falls back
to typescript/lib/tsc when @typescript/native is absent, so downstream apps get
the faster build without a hard requirement on TypeScript 7.

A cold build of the monorepo drops from ~10.7s to ~2.1s.

TypeScript 6/7 changes that required source updates

• moduleResolution: node (node10) was removed. Dropped from
  tsconfig.common.json and from the CLI project template. The default resolver for
  module: commonjs honors exports maps, so @loopback/graphql no longer imports
  Middleware from a deep type-graphql path (that path is not exported) and
  declares the type itself.
• @types/* packages are no longer auto-included. This accounted for 5630 of the
  5668 initial errors (describe, process, NodeJS all unresolved);
  tsconfig.common.json now lists types: ["node", "mocha"].
• Reading a parent class field through super is an error (TS2855). cron
  declares fireOnTick as a field but installs it on the prototype, so
  @loopback/cron now calls through BaseCronJob.prototype.
• Declaration emit no longer adds /// <reference path> for ambient files.
  TypeScript 5.2 emitted one into testlab/dist/expect.d.ts, which is how consumers
  resolved the global Internal type. Without it, expect silently becomes any in
  every consuming package and api-extractor fails with
  Unable to follow symbol for "Internal". should-as-function.d.ts therefore moves
  to src/should-as-function.ts and exports its types as a module.

Lint

@typescript-eslint moves to v8 — v7 caps at typescript <5.6.0 and does not support
TypeScript 6. Rules that v8 renamed or split are disabled to preserve the rule set this
config already had (no-var-requires → no-require-imports, ban-types → its three
successors); that covered 1135 of 1232 findings. The remaining 97 are fixed in code.

v8's no-misused-promises also crashed on cli-main.js, which used a top-level
CommonJS return — the rule assumes every return has an enclosing function. That is
restructured as if/else.

Defects found along the way

• belongs-to-repository-factory.unit.ts never assigned companyRepo; its stub helper
  assigned customerRepo twice, clobbering the previous beforeEach.
• rest.application.ts declared the same route(verb, path, spec, handler) overload
  twice.
• lb4 app generated process.env.HOST || '127.0.0.1', so every newly scaffolded app
  failed its own npm run lint. The adjacent PORT line already used ??.
• bin/sync-dev-deps.js had been broken since the Lerna → npm workspaces migration
  (d5c4994 removed loadLernaRepo); repaired with the @npmcli/map-workspaces
  pattern already used by update-template-deps.js, since propagating the new spec
  depends on it.

Behavior notes

The || → ?? conversions touch framework code. No boolean operand was converted, so
false ?? true cannot bite. Two numeric operands now honor 0:
examples/rpc-server (port: 0 means an ephemeral port) and http-caching-proxy
(error.statusCode). Nine string sites now honor an explicit ''. The rest are arrays
and are equivalent.

Verification

Check	Result
Cold build	clean, ~2.1s (was ~10.7s)
CI package tests	3572 passing, 0 failing
CI extension tests	233 passing, 0 failing
CI example tests	346 passing, 0 failing
npm run lint	clean
api-extractor / tsdocs	clean; docs/apidocs output byte-identical
npm ci + check-package-metadata	clean
Scaffolded lb4 app	builds on TS7; tests, eslint and prettier clean

Pre-existing and unrelated: packages/cli/test/** generator tests time out locally
(CI does not run that glob), and packages/cli/.yo-rc.json is stale — --meta
regenerates 126 lines of difference with or without this change.

Checklist

• DCO (Developer Certificate of Origin) signed in all commits
• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

🤖 Generated with Claude Code