feat: bound default output instead of dumping every string #202

Problem statement

Running stringy on a real binary with no flags dumps every extracted string to the terminal. On a debug build of stringy itself:

target/debug/stringy target/debug/stringy    # prints 47,820 rows

The whole premise of the tool is "meaningful strings, ranked" -- but the default behavior buries that behind tens of thousands of lines. A user's first-ever run floods their scrollback and undersells the ranking that already exists internally.

Proposed solution

Apply a sensible default output bound when --top/--raw are not specified. Options:

• Default --top to a reasonable N (e.g. 100-200) for TTY output, and print a footer like ... 47,620 more (use --top N or --raw for all).
• Consider making the cap TTY-aware: bounded when stdout is a terminal, unbounded when piped (so | grep, | jq still see everything). This mirrors how pagers/git behave.

Touches: pipeline (filtering/limit), main.rs (default value + TTY check), output (footer line).

Alternatives considered

• Keep unbounded default, rely on users to pipe to head/less: poor first-run UX; the tool should be usable without knowing the flags.
• Always cap regardless of piping: breaks | jq/| grep pipelines that need the full set.

Area

Pipeline / CLI