[wrangler] Fix case-insensitive-env leaking stale duplicate keys on override

[mittalpk]

Fix case-insensitive-env.ts leaking stale, differently-cased duplicate keys.

On Windows, wrangler loads .env values through a case-insensitive Proxy wrapper (packages/wrangler/src/config/case-insensitive-env.ts) so lookups like env.PATH and env.Path resolve to the same value, and this object is assigned directly to process.env (packages/wrangler/src/config/dot-env.ts). When a key is set again under a different casing (e.g. .env.local overriding a value from .env with different casing), the previous casing's property was never removed from the underlying target object. get/has still resolved correctly through the internal tracking map, but anything that enumerates process.env — Object.keys, for...in, JSON.stringify, object spread, or a spawned subprocess inheriting the environment — saw both the stale and current key.

The set, defineProperty, and deleteProperty traps now keep exactly one own-property per case-insensitive key, so enumeration always reflects only the current value. (deleteProperty had the same class of bug in the other direction: it deleted from the internal tracking map by canonical key but issued Reflect.deleteProperty using whatever casing the caller passed, so delete env.path after env.PATH = ... left an orphaned, untracked PATH property on the target — fixed the same way, by resolving the tracked casing first.)

Repro (before the fix):

const env = caseInsensitiveEnv();
env.PATH = "1";
env.Path = "2";
Object.keys(env); // ["PATH", "Path"] — should be ["Path"]
JSON.stringify(env); // {"PATH":"2","Path":"2"} — should be {"Path":"2"}

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: internal bug fix, no user-facing API/behavior change beyond correcting the leak

---

[changeset-bot]

🦋 Changeset detected

Latest commit: a3c5e60

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
wrangler	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

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[workers-devprod]

Codeowners approval required for this PR:

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• .changeset/case-insensitive-env-stale-keys.md: [@cloudflare/wrangler]
• packages/wrangler/src/tests/case-insensitive-env.test.ts: [@cloudflare/wrangler]
• packages/wrangler/src/config/case-insensitive-env.ts: [@cloudflare/wrangler]

[workers-devprod]

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• ✅ @cloudflare/wrangler

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[workers-devprod]

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commit: a3c5e60