docs: correct v2.0.0 release notes — drop deferred electron-updater claim, fill Phase D section

Two staleness items in the shipped v2.0.0 docs:

1. README's Version History bullet for v2.0.0 listed
   'electron-updater integration' among the deliverables, but
   electron-updater was explicitly deferred to v2.1 (the in-app
   notifier badge handles the 'tell users a new version exists'
   path; auto-install is the v2.1 work). Replaced with 'real
   installers across macOS / Linux / Windows' which is what
   v2.0.0 actually shipped.

2. CHANGELOG.md v2.0.0 Distribution section was a literal TODO
   placeholder '*(see Phase D commit notes when they land)*' that
   got shipped as-is. Filled in with the actual Phase D content:
   electron-builder metadata polish, 1024×1024 icon regeneration,
   release-notes template rewrite, signing decision, and the
   electron-updater-deferred-to-v2.1 note.

No code change. Both fixes only affect the rendered README and
CHANGELOG on GitHub.

Author: DeceasedCranium

CHANGELOG.md

@@ -78,7 +78,24 @@ gap that would have embarrassed us in front of a new user.
   direction: rtl` pattern.
 
 **Distribution:**
-- *(see Phase D commit notes when they land)*
+- electron-builder `build` block fleshed out — explicit `icon: assets/icon.png`
+  for all three platforms (electron-builder generates `.icns` / `.ico` /
+  256-px desktop icons from the source PNG), Linux desktop entry with
+  `GenericName` + `Keywords` so KDE/GNOME launchers index the app, .deb
+  metadata with synopsis + long description, NSIS installer config
+  (custom install dir, preserve user data on uninstall), DMG title with
+  version, `copyright` + `author` + `license: MIT` fields.
+- Source icon regenerated at 1024×1024 (was 256×256) so macOS .icns
+  generation succeeds.
+- Release-notes template in `.github/workflows/release.yml` rewritten —
+  documents the unsigned-binary workarounds for macOS Gatekeeper and
+  Windows SmartScreen explicitly, points at CHANGELOG.md instead of the
+  old README#version-history anchor.
+- macOS / Windows code signing deferred — paid certs aren't worth it
+  for a personal-use project; documented workarounds inline.
+- electron-updater deferred to v2.1. The existing in-app update notifier
+  (polls api.github.com once per launch) handles the "tell users a new
+  version exists" path; one-click auto-install is the v2.1 enhancement.
 
 ## v1.14.0 — Personalized Show of the Day
 

README.md

@@ -157,7 +157,7 @@ Short version: Electron main process owns filesystem / OS / Cast / MPRIS / signi
 
 See [`CHANGELOG.md`](./CHANGELOG.md) for the full per-release log going back to v1.0. Recent highlights:
 
-- **v2.0.0** — Distribution release. Polish + stability + identity pass: storage-bug audit, sidebar layout fix, debug-gated console, friendly error messages, About panel, first-run experience, README + screenshots, AppImage as primary Linux artifact, electron-updater integration. No new user-facing features beyond what shipped in v1.x — this is the "ready to share with friends" milestone.
+- **v2.0.0** — Distribution release. Polish + stability + identity pass: storage-bug audit, sidebar layout fix, debug-gated console, friendly error messages, About panel, first-run experience, README + screenshots, AppImage as primary Linux artifact, real installers across macOS / Linux / Windows. No new user-facing features beyond what shipped in v1.x — this is the "ready to share with friends" milestone.
 - **v1.14.0** — Personalized Show of the Day with For You / Global toggle and reason chips.
 - **v1.13.0** — setlist.fm live integration: authoritative per-song play counts.
 - **v1.12.0** — Setlist Intelligence kickoff: Songs tabs, attendance tracking, title dedup.