Add --imports / --exports / --symbols CLI convenience flags #208

Summary

Add convenience CLI flags --imports, --exports, and --symbols as shorthands for existing tag filters. This is the one literal acceptance criterion from the v0.2 epic (#40, Feature 3) intentionally deferred in favor of the generic tag system.

Current behavior

Imports, exports, and demangled symbols are fully extracted, tagged, classified, and ranked. They are filterable today only via the generic tag flags:

stringy bin --only-tags Import
stringy bin --only-tags Export
stringy bin --only-tags DemangledSymbol

Proposed

Add boolean convenience flags in src/main.rs mapping to the tag filter:

• --imports -> --only-tags Import
• --exports -> --only-tags Export
• --symbols -> --only-tags DemangledSymbol (or Import+Export+DemangledSymbol -- decide during design)

Design notes / co-change requirements:

• Follow clap-derive conventions in main.rs; push conflict handling into clap (conflicts_with for --only-tags/--no-tags/--raw as appropriate).
• Define composition semantics with --only-tags (likely conflict, matching --raw's pattern).
• Update tests/integration_cli.rs and the CLI-flag table in AGENTS.md (GOTCHAS.md notes these must co-change).
• Long-only flags (consistent with --enc/--yara/--raw); no short flags for infrequent options.

Acceptance criteria

• --imports, --exports, --symbols implemented as clap flags
• Conflict rules with --only-tags/--no-tags/--raw defined and enforced by clap
• AGENTS.md CLI-flag table updated
• tests/integration_cli.rs covers each new flag
• just ci-check passes

Context

Follow-up to #40 (Feature 3). Extraction/tagging/ranking are already complete; this is CLI ergonomics only.