typescript: give declaration compiles a types-only view of npm packages

[slarson-redo]

typescript: give declaration compiles a types-only view of npm packages

Problem

A TypeScriptCompile{,Native} action's inputs include TsInfo.transitive_files of every dependency. For an npm package that is the whole package tree (:files, a copy_directory of src/): JS, maps, docs, tests. Bazel expands trees in the sandbox, so each action symlinks and prefetches every file of every transitive npm package. On redo's type-check chain that is 128-153k input files per action, 84% of them npm, while tsgo opens ~5k.

Change

• typescript/npm_plugin.bzl: each TS npm spoke also builds :types, a copy_to_directory of :files filtered to **/*.{ts,tsx,mts,cts} and **/*.json (package.json for resolution and package scope, other JSON for resolveJsonModule imports); ts_import(declarations = [":types"], types = ":types"). A package whose only declarations are .d.cts/.d.mts is now treated as a TypeScript package too (previously a redo-local patch).
• typescript/rules.bzl: ts_import gets a types attr (it requires root, and fails without one). The package struct gets types_path (create_package), TsInfo is built without the root's descriptors (for npm they are the full :files tree, which would otherwise stay an input), and the compile package manifest uses types_package_path (types_path or path). The manifest already separates id from path, so the dependency graph is untouched; stage-nm and the tsconfig paths resolve into the smaller tree.
• TsCompilerInfo.runtime_ts: the compiler runtime (tslib) is CjsInfo+JsInfo only, so its types tree would be missing; its TsInfo is added to compile inputs and TsCompileInfo.declarations (lint).
• Runtime paths (JsInfo, CjsInfo, nodejs/jest/webpack) are unchanged.

Results (redo monorepo)

Input files per declaration action (aquery + tree counts, verified exact against materialised trees):

action	before	after
agents/platform-agents:lib	145,633	69,171 (-52%)
merchant/server:lib	153,421	76,461 (-50%)
order-editing/service:lib	128,591	61,189 (-52%)
orders/service:lib	65,330	32,854 (-50%)

All 10,045 native compile actions: p50 30.5k -> 15.4k, p90 104k -> 51k, aggregate -50.5%.

CI-shaped A/B (real MR chain, CI flags, --jobs=28, fresh output base, warm disk-cache seed, 5 reps each, Coder 16 CPU, processwrapper-sandbox), critical-path declaration actions:

	before	after
CP declaration time	728.9 s	620.9 s (-15%)
input prefetch	91.8 s	39.0 s (-58%)
sandbox setup (createFileSystem)	85.3 s	45.2 s (-47%)
compiler	354.2 s	347.0 s (-2%)
Bazel wall (median)	858 s	787 s (-8%)

Correctness: //:dts plus scoped and 14 extra tslint targets (tsgo and node tsc) pass with 0 errors, and all 61,633 emitted .d.ts/.d.cts/.d.mts are byte-identical (sha256) to the previous build.

Known difference

A JS-only subpath of a package that also ships some .d.ts no longer resolves to an untyped JS file; it is "not found". Both are errors under strict settings and none exists in redo. allowJs on a ts_library's own JS sources still works (covered by a test): declaration compiles never analyze npm JS (maxNodeModuleJsDepth 0), so the only effect is that JS-only npm subpaths are not found.

Same cause, seen in rules_javascript's own tests: rxjs 7.4.0 has no types exports condition, so under bundler resolution it only "resolved" by finding its JS (implicitly any). It is now not found, so the test fixture moves to rxjs 7.8 (declares types).

Also fixed

• bazel_lib 3.2.1's copy_to_directory opts into path mapping but writes unmapped paths into its config JSON, so :types failed under --experimental_output_paths=strip (rules_javascript's preset; redo runs with it off). bazel_lib 3.5.0 (what redo pins) drops path mapping for that action; rules_javascript now requires it.
• angular_library compiles use the types-only package paths, like ts_library.

Cost

Keeping all JSON (not just package.json) adds ~1.3% to the types trees (284 of 21,279 files over 721 trees in orders/service + s3-client + react/animation), so the input counts above rise by roughly that. One extra copy_to_directory action per npm package a compile touches (+5.7% actions). Cacheable; cold cost was ~3.7% of action time once. Declaration compile cache keys all change on adoption (one full rebuild).