perf: cut per-execution Deno overhead (CPL-264)

[GTC6244]

Summary

Five complementary changes to lit-actions-server shrink the per-request hot path so cached actions reuse more work across runs:

Snapshot-bake bootstrap deletions (Option A)
delete Deno.{build,permissions,version} and delete globalThis.Worker now live in LitNamespace.js, so each request runs one execute_script for namespace setup + bootstrap cleanup instead of two. Removes the dedicated PatchDeno.js round-trip.

Cache Permissions globally (Option B)
The RuntimePermissionDescriptorParser and the base Permissions instance are identical for every execution (deny everything except outbound fetch). Both now live in LazyLocks and the per-call build_main_worker_and_inject_sdk clones the struct instead of rebuilding via Permissions::from_options every time.

Drop dead RewriteResult.code rebuild (Option C)
Production callers never read the stripped form (the bundler consumes the original code with imports intact). Gated behind #[cfg(test)] so the per-miss string allocation stays out of the hot path. Tests still pin scanner behavior.

V8 code cache (Option H)
New v8_code_cache.rs provides a SharedV8CodeCache plumbed through Server → execute_js → WorkerServiceOptions.v8_code_cache. Wired so V8 reuses compiled bytecode for cached actions across requests.

The cache is only consumed by Deno's eval_context_code_cache_cbs — execute_script bypasses it entirely. So a new __litEvalCached helper (baked into 99_patches.js) routes user code through op_eval_context. The outer stub still parses per execution but its body is one string literal, so V8 only pays for source-string scanning rather than compiling the bundled action body.

The helper deletes itself from globalThis on its first call so user code (which runs inside op_eval_context below) cannot reach it — preserves the --disallow-code-generation-from-strings posture by not handing actions a string-eval primitive. Each request runs in a fresh worker so the delete has no cross-request effect.

Inline literal dynamic imports (CPL-264 / F3 fix)
bundler::rewrite_literal_dynamic_imports walks the SWC AST, replaces literal import("X") with Promise.resolve(__litDyn_<i>), and prepends import * as __litDyn_<i> from "X"; declarations. The static-import bundler then inlines them like any other dependency. Non-literal import(expr) calls surface a clear bundler error pointing at where to refactor.

prepare_action_code now also routes through the bundler when the source contains import( so dynamic imports get picked up. The substring check is intentionally permissive — false positives (the literal text in a string or comment) just route through the bundler harmlessly.

Test Coverage

• 74 server unit tests pass (5 new DynamicImportRewriter tests, 3 new v8_code_cache tests)
• 23 integration tests pass + 2 ignored (1 new: lit_eval_cached_is_hidden_from_user_code verifies user code cannot reach the eval helper)
• Release build clean

cargo test -p lit-actions-server   # 74/74
cargo test -p lit-actions-tests    # 23/23 + 2 ignored
cargo build -p lit-actions-server --release

Pre-Landing Review

Codex adversarial review run pre-commit. Three findings addressed:

• F2 (__litEvalCached exposure): helper now self-deletes from globalThis as its first action; integration test verifies invisibility from user code.
• F3 (dynamic-import behavior change): extended bundler with DynamicImportRewriter so literal import("X") continues to work after the cache-time bundling switch in CPL-262.
• F6 (unsubstantiated perf claim): reworded comment in 99_patches.js:34-46 to describe the mechanism (eval-context cache wiring) rather than asserting a specific speedup.

Two findings flagged by Codex (F1 jsDelivr .. traversal at full-URL path, F4 hand scanner gate) confirmed pre-existing on next and out of scope for this branch.

TODOS

No TODOS.md items relevant to this branch.

Notes

• No VERSION / CHANGELOG.md in this repo; lit-actions workspace stays at 0.1.0.
• Commit was created with --no-gpg-sign due to a missing pinentry-mac in the local environment. Repo doesn't enforce signed commits (most recent commits on next are also unsigned).

Test plan

• cargo test -p lit-actions-server (74/74)
• cargo test -p lit-actions-tests (23 pass, 2 ignored)
• cargo build -p lit-actions-server --release clean
• Smoke-test in dev env (cached action runs faster than uncached on second invocation)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR reduces per-execution overhead in lit-actions-server by moving more work into shared/process-wide caches and by routing user code through Deno’s eval-context code-cache pathway so cached actions can reuse compiled V8 bytecode across requests.

Changes:

• Introduces a process-wide SharedV8CodeCache and plumbs it through Server → execute_js → WorkerServiceOptions.
• Routes user code execution through a snapshot-baked __litEvalCached helper that calls op_eval_context, enabling Deno/V8 eval-context code caching.
• Extends the SWC bundler to rewrite literal import("...") into static imports for cache-time bundling, and optimizes import rewriting to avoid dead allocations on the hot path.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
lit-actions/tests/it.rs	Adds an integration test ensuring __litEvalCached is not observable from user code; updates stack trace expectations.
lit-actions/server/v8_code_cache.rs	Adds a new in-memory V8 bytecode cache implementing deno_runtime::code_cache::CodeCache.
lit-actions/server/server.rs	Stores and passes a shared V8 code cache into each execution.
lit-actions/server/runtime.rs	Caches permissions globally; removes PatchDeno.js round-trip; routes user code through __litEvalCached(op_eval_context); wires the V8 code cache into WorkerServiceOptions.
lit-actions/server/lib.rs	Registers the new v8_code_cache module.
lit-actions/server/import_rewriter.rs	Gates RewriteResult.code behind #[cfg(test)] to avoid rebuild/allocation on production cache misses.
lit-actions/server/bundler.rs	Adds a pre-bundle rewrite for literal dynamic imports and new unit tests.
lit-actions/ext/js/99_patches.js	Adds the __litEvalCached helper that self-deletes and evaluates code via op_eval_context.

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