fix(env): proxy directly to process.env instead of snapshotting

[jerome-benoit]

Issue for this PR

Closes #22451

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The Env service was snapshotting process.env at init time via InstanceState.make(() => Effect.succeed({ ...process.env })). This caused stale reads (Env.get() returned the init-time value, not the current one) and silent set() calls (only the internal copy was mutated, never process.env).

The fix replaces the InstanceState-based snapshot with a Layer.succeed that proxies directly to process.env via Effect.sync:

• get(key) → Effect.sync(() => process.env[key]) — live read
• all() → Effect.sync(() => ({ ...process.env })) — fresh shallow copy per call (prevents accidental mutation of process.env via the returned object)
• set(key, value) → Effect.sync(() => { process.env[key] = value }) — writes to process.env directly
• remove(key) → Effect.sync(() => { delete process.env[key] }) — deletes from process.env directly

The Env.Interface contract is unchanged — zero consumer modifications needed.

Additionally:

• Removed 2 obsolete TODO workaround comments in provider.ts that documented the now-fixed bug
• Added 5 missing env var cleanups in test/preload.ts (AICORE_*, AWS_CONTAINER_*) to prevent host env leaking into tests

How did you verify your code works?

• bun typecheck passes across all 19 packages
• Verified all env.all() / env.get() consumers in provider.ts, config.ts, and tool/registry.ts are read-only and unaffected by the change from snapshot to live proxy
• Cross-validated that no production code depends on snapshot (frozen-at-init) semantics — all accesses are immediate reads, never stored or compared across time
• Confirmed the 6 existing test env save/restore patterns (preload.ts, beforeEach/afterEach, try/finally, helper closures, Effect.acquireRelease, afterAll) all operate on process.env directly, independent of Env.Service

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Migrate all process.env to Env namespace for consistent caching (#12698) doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

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