feat: add generic JSONL CLI vertical slice

[karngyan]

Summary

Implements logical PR 3 from the Milestone 1 roadmap.

• add reusable streaming generic AEP JSONL import services in autophagy-core
• add the autophagy import, autophagy sessions, and autophagy search commands
• support file and stdin input, stable source identities, exact project selection, and dry-run
• continue past record-level parser/validation conflicts with bounded line diagnostics
• provide text and tagged JSON output with explicit exit-code semantics
• preserve duplicate imports as no-ops and surface quarantined conflicts
• add an anonymized demo corpus, user guide, and README quickstart
• expand documentation parsing to every Markdown file under docs/

Privacy defaults

• dry-run never opens or creates a database
• raw event JSON and tool input are not copied into FTS5 by default
• tool input indexing requires --index-tool-input
• metadata indexing requires an explicit repeatable --index-metadata KEY
• project selection is exact and repeatable through --project PATH

Verification

• mise run check
• 18 tests across AEP, storage, importer, and end-to-end CLI behavior
• file import → sessions → search → duplicate reimport exercised through the built binary
• rejected dry-run records return JSON diagnostics and exit code 2 without creating a database
• manual demo corpus import, session listing, evidence-ID search, and duplicate reimport
• strict Clippy and rustdoc with warnings denied
• actionlint
• git diff --check