c1-literals: governed egress's host fault names its task, not a plane word

[MattJackson]

Drains the c1-literals row crates/busbar-kernel/src/plane_host/egress.rs | streaming.

• plane_host/egress.rs:822: the host fault text "could not start its streaming task" now reads "could not start its stream task".
  • The text is 1.6.0-only: the plane-host egress fault cause, with no 1.5.5 oracle cell.
  • No test reads it.
  • "streaming" is a plane name in the c1 vocabulary.
• The row is struck from qa/c1-literals.toml in the same commit, since that ledger is drain-only.
• This PR adds or changes no law0 hits.
• Its hunk is disjoint from row 74 F25: the door path's jwt-bearer mint keeps 1.5.5's raw aud, the stripped dial and the Basic #922, row 74 F25: a lane base URL's userinfo is stripped, never dialled, sent or printed, as 1.5.5 did #876 and row 166: strike the unserved plane FFI subprocess spawn path (its env secret resolved at the spawn) #866, which edit the same file at lines 558 and 666-668.

The rest of c1-literals waits on the coordinator's seam rulings. Nothing was run locally; CI is the proof.