[PoC / do-not-merge] R30: verify clean per-instance receiver attribution in CI

[vringar]

Proof-of-concept — DO NOT MERGE (R30 verification only)

This draft exists solely so CI can execute test_poc_receiver_attribution.py — the sandbox couldn't spawn the browser to run it end-to-end.

What it tests: whether the stealth instrument can record per-instance receiver attribution — via a module-local WeakMap<receiver, id> held in the isolated content-script world, emitting <Interface>#<id> in the existing receiver column — while staying clean/undetectable (no page own-property, no leaked global, prototype wrapper byte-for-byte unchanged).

Why: to empirically disprove (or vindicate) ADR-0001 gap #2's claim that per-instance attribution requires mutating the instance. The crux (is the Xray this a stable WeakMap key?) resolves yes by SpiderMonkey's per-compartment wrapper-map guarantee; this PR is the executed confirmation the maintainer asked for.

Read the result as: test_poc_receiver_attribution.py green = 2 distinct XMLHttpRequest#<n> ids, a twice-called instance collapsing to one id, and the clean/undetectable vectors all passing. Other test failures are expected — the PoC changes the receiver emission format, which is throwaway, not production.

DO NOT MERGE. This is a measurement/verification vehicle for an ADR decision; the real follow-up (if disproven) is a small ADR wording correction, not this code.

[codecov]

Codecov Report

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Additional details and impacted files

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