Add massive neutrino support and improve CSV/CLI output

- Add neutrino mass parameter to SpectrumConfig and CLI interface
- Update PhaseSpace component to handle neutrino mass effects properly
- Update CSV headers to show basic endpoint and all transition types
- Add --csv-verbosity option to CLI with 'full' and 'concise' options
- Fix comparison plots to properly show linear scale variations
- Add comprehensive tests for neutrino mass functionality

.llm-wiki/meta/log.md

@@ -0,0 +1,25 @@
+# Activity Log
+
+> Auto-generated from meta/events.jsonl. Do not edit manually.
+
+## [2026-05-27T11:55:40.409Z] bootstrap
+- topic: "Beta Spectrum Calculator — High-precision beta decay spectrum simulation for ⁹⁹Tc and other forbidden decays", mode: "personal"
+
+## [2026-05-27T11:55:55.301Z] capture
+- source_id: "SRC-2026-05-27-001", file_path: "/home/unzhakov/workspace/beta_shape_pnpi/docs/gA-extraction/01-ssm-algorithm.md", format: "markdown"
+
+## [2026-05-27T11:56:08.796Z] capture
+- source_id: "SRC-2026-05-27-002", file_path: "/home/unzhakov/workspace/beta_shape_pnpi/docs/nuclear-structure/01-shape-factors.md", format: "markdown"
+
+## [2026-05-27T11:59:21.939Z] capture
+- source_id: "SRC-2026-05-27-003", url: "https://jyx.jyu.fi/bitstreams/eb3a10c8-b94c-4009-8a8e-839bfddc7c58/download", format: "web"
+
+## [2026-05-27T12:00:22.177Z] capture
+- source_id: "SRC-2026-05-27-004", url: "https://cea.hal.science/cea-04796921/file/PhysRevC.110.055503.pdf", format: "web"
+
+## [2026-05-27T12:01:29.331Z] capture
+- source_id: "SRC-2026-05-27-005", url: "https://arxiv.org/pdf/2506.17544", format: "web"
+
+## [2026-05-27T12:01:51.914Z] capture
+- source_id: "SRC-2026-05-27-006", url: "https://arxiv.org/pdf/2312.07448", format: "web"
+