perf(bedrock): add SKILLSPECTOR_COMPACT_PROMPTS option to reduce LLM token usage - #457

Introduce an opt-in env var (SKILLSPECTOR_COMPACT_PROMPTS=true) that reduces
token consumption across all LLM analyzer prompts while preserving the
default behavior for backward compatibility.

When enabled, compact mode applies five optimizations:

1. Line numbers drop zero-padding (L001 -> L1), saving ~3 chars per line
2. Meta-analyzer finding context omitted from prompt (already in file content)
3. Meta-analyzer response schema drops unused OverallAssessment field
4. All analyzer prompts condensed (redundant phrasing, verbose formatting)
5. BASE_ANALYSIS_PROMPT output guidelines shortened from 5 lines to 2

Estimated per-scan savings with compact mode on:
- ~100 input tokens/call from prompt condensation (x4-8 calls)
- ~3 chars/line from line numbering (500-line file = ~375 tokens/call)
- ~30-50 output tokens/call from OverallAssessment removal
- Variable savings from context field omission

Default behavior is fully preserved: all original prompts, schemas, and
formatting remain active unless the env var is explicitly set.

All 2955 tests pass in both default and compact modes. Lint clean.

Signed-off-by: leonardogasparini <leonardo.gasparini@tui.com>