Improve capture safety and guided CLI usability

[jakthom]

Recording could silently replace an existing capture, unsupported inputs could appear successful, and errors ended the guided workflow. This change protects recordings and carries the command center through execution, results, and recovery.

• Require --overwrite for existing recording destinations and reject input/output identity, including symlinks and hard links. Preserve buffered data when stopping a recording.
• Reject empty or unsupported captures with actionable errors, validate filters and gateway addresses, and identify undecodable PGNs in validation results.
• Correct Tab completion and Escape behavior, number workflow shortcuts, and keep controls visible in compact terminals.
• Add progress and saved-file feedback, keep settings for editing and retrying, and let Ctrl+C stop a run while keeping the interactive session open.
• Add PGN search by name, filesystem completion, readable device/schema tables, and accessible command previews. Update the README and terminal illustration.

Compatibility: scriptable commands continue to default to JSON; guided workflows default to readable text. Validation JSON adds undecodableByPgn. Existing output files require explicit replacement, and empty/unsupported captures now fail instead of silently returning no results. JSONL recordings remain an export format and are explicitly identified as unsupported replay input.

Validation:

• go test -race ./..., including 16 new usability regression tests with additional cases for linked paths and capture formats.
• golangci-lint run ./..., govulncheck ./..., and gosec -quiet -exclude-dir=.claude -exclude=G115 ./... passed.
• Linux and Windows test binaries compiled successfully.
• Real terminal sessions exercised completion, filtered Escape behavior, 40×12 layouts, recording cancellation and save, overwrite confirmation, retained-settings recovery, and accessible preview/run prompts.

Live marine hardware and screen-reader software were not tested.