Config: one authority — shrink tui/src/config* to an adapter over crates/config

From the 0.9.14 refactor backlog.

`tui/src/config.rs` (~13.3k) + `tui/src/config/` + `config_persistence.rs` sit alongside `crates/config` (~46.9k). The provider-wire-collapse lane already moves route resolution into the crate; keep going until `tui/src/config*` is a thin adapter or gone. #6034 records that `crate::config` is the hub of the 118-module cycle blocking TUI decomposition, so this is also the prerequisite edge-cut for #5316.

Size: L; can run in parallel with the engine extraction if ownership is path-disjoint.

Start by comparing tui/src/config.rs, tui/src/config/, and config_persistence.rs with crates/config, then read #6034 for the 118-module cycle and the route-resolution work. Done means tui/src/config* is reduced to a thin adapter over crates/config or removed, while preserving the edge-cut needed for TUI decomposition in #5316.

Written by the indexing model from the issue text.