refactor: centralize application effects

[zatevakhin]

what changed

• add a private application boundary with typed AppEvent, RuntimeEvent, and ordered Effect values
• migrate key, mouse, ACP, connection, supervisor, tick, and runtime-result dispatch through application::update
• move command dispatch, persistence, clipboard, external editor, terminal redraw, and quit handling to the runtime effect executor
• preserve ACP/runtime channels, command payloads and ordering, persistence schema, status strings, and phase 4 state owners
• reconcile the inherited duplicate application test modules into one focused 16-test suite

validation

• cargo fmt --all -- --check
• cargo check --all-targets --all-features
• cargo clippy --all-targets --all-features -- -D warnings
• cargo build --all-targets --all-features
• cargo test --all-targets --all-features (902 passed)
• git diff --check

boundary proof

• exactly one private mod application, one AppEvent, one Effect, and one application::update
• exactly eight phase 5 source files changed
• zero command sender parameters, direct command sends, config writes, clipboard launches, pending command queues, or direct quit mutation in handlers
• Command definitions and phase 6 ACP transport files are unchanged
• App remains 13 direct fields; all 12 phase 4 owner modules remain private; four phase 11 compatibility forwards remain

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