Artifact receipts live only in memory, so files left behind by a dead
process were unreachable but persisted forever despite the advertised
300s TTL — a retention failure on the surface meant to be ephemeral
(blocker 4 of andrexibiza's #91535 review). A fresh ArtifactStore now
removes every artifact-id-shaped file and stale *.tmp with no index entry
(at construction the index is empty, so all such files are orphans).
Non-artifact-shaped names are untouched. Regression: store -> recreate
store over same root -> orphan+tmp gone, unrelated file kept.
Addresses both merge blockers from @andrexibiza's review of #85351:
1. HTTP-uploaded artifacts could never be consumed by broker dispatch:
artifact_scope_key hashed (principal, session, family), the HTTP routes
store with an EMPTY session (API-key auth has no server session) while
broker validation carries a session-bearing ControllerScope — every
real upload->dispatch journey died with ArtifactScopeMismatch
(reproduced before fixing). Canonical ownership is now
principal/transport-family (documented in the scope-key docstring);
ids stay unguessable server-minted 32-hex and downloads one-shot.
New composition regression: HTTP-shape upload -> registered controller
scope -> broker artifact dispatch, mutation-checked (re-adding session
to the key makes it fail).
2. The 'profile-scoped' artifact store was first-profile-wins process
state: one adapter-level singleton pinned profile B to profile A's
physical root on multiplex listeners (same frozen-handle class as
#88734). Stores are now cached by resolved profile, and the broker
selects the store from the controller scope's profile_id (default-slot
fallback preserves single-profile/test behaviour). New A/B multiplex
regression proves distinct physical roots regardless of touch order.
Also documents the advertised ticket_expires_at as best-effort wall clock
(broker enforces expiry monotonically) per review feedback.
kshitijk4poor