feat(vault): M5 slice 2 — TUI reveal + agent-side clipboard copy #10

Job	Run time
cargo-audit	3m 13s
clippy	39s
vault --version emits §13.2 attribution	42s
rustfmt	16s
test (macos-latest)	1m 20s
test (ubuntu-latest)	55s
cargo-deny	36s
	7m 41s

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