chore: v0.4.0 — bump version + CHANGELOG entry

manifest.json version 0.3.0 → 0.4.0. CHANGELOG.md entry for v0.4.0
documents the first-run UX hint feature (merged in b82f14e via
v0.4.0-prep branch). Zero new permissions, zero new dependencies,
zero behaviour change for existing users.

Shipped the same day v0.3.0 went LIVE on Chrome Web Store
(~15.5h after submission). Same-account update review window is
~24-48h per the reference_chrome_web_store_rules memory.

CHANGELOG.md

@@ -7,11 +7,60 @@ Format: [Keep a Changelog 1.1.0](https://keepachangelog.com/en/1.1.0/) — versi
 
 ## [Unreleased]
 
-### Planned — Tier 3 (Chrome Web Store submission)
-- Listing assets: 1280x800 screenshots, 440x280 promo tile
-- Privacy policy URL published at `davidtkeane.com/rangerhq-tuner/privacy`
-- 2-Step Verification on Google account
-- $5 dev fee + submission
+### Planned — Tier 2 polish (next)
+- Light mode support (`prefers-color-scheme` + flipped palette across popup / NewTab / Options)
+- `.m3u` parser alongside `.pls` to widen future-adapter compatibility
+- Station artwork lazy-load + fallback to family helmet
+- Better error UI for failed streams ("Stream unavailable, try another")
+- `.crx` packaging instructions in README for sideload users
+
+---
+
+## [0.4.0] — 2026-06-09 — First-run UX hint
+
+First post-launch update, shipped the same day v0.3.0 went LIVE on the Chrome Web Store. Pure UX polish — zero new permissions, zero new code dependencies, zero behaviour change for existing users.
+
+### Added — Discoverable "pick a station to begin" affordance
+
+Triggered by David's own 30-second panic on first Web Store install (uninstalled the dev build, installed from the Web Store fresh, hit Play, got nothing, then realised "ah, I need to pick a station first"). The product worked correctly — the dev build had a seeded station from hours of testing, the fresh install does not — but the 30-second panic exposed a real first-run-UX gap.
+
+**Two layered cues, both pure CSS driven by a `body.is-first-run` class:**
+
+1. **Subtle accent-green glow pulses** around the station list (popup) and the Quick Stations chip row (NewTab). Uses a 2.4-second `box-shadow` keyframe at low alpha (0.18-0.25) — visible but not noisy.
+2. **Bouncing ↓ arrow** appended to the "Pick a station to begin" text in both surfaces. Uses an `::after` pseudo-element with a 1.8-second `translateY` keyframe.
+
+The `is-first-run` class is toggled by a tiny `reflectFirstRunHint()` function called from:
+- `init()` once stations + `currentStation` are resolved
+- `onPickStation()` the moment a user picks
+- the `chrome.storage.onChanged` listener when another surface picks (so the hint disappears on both surfaces simultaneously via cross-surface sync)
+
+Existing users with a stored `tuner.currentStationId` never see either cue — the class only attaches when `currentStation` is null.
+
+### Files touched
+
+- `src/popup/popup.css` (+35 lines — keyframes + `.is-first-run` rules)
+- `src/popup/popup.js` (+11 lines — `reflectFirstRunHint()` + 3 call sites)
+- `src/newtab/newtab.css` (+36 lines — same idea, NewTab-namespaced)
+- `src/newtab/newtab.js` (+10 lines — same pattern)
+
+Total: 4 files, +92 lines, 0 deletions.
+
+### Not changed
+
+- No new permissions
+- No new host_permissions
+- No new external libraries
+- No change to `manifest.json` beyond the version bump and CHANGELOG-referenced URL
+- No data migration required (no storage shape change)
+
+### Same-day context
+
+This update ships the same day:
+- v0.3.0 went LIVE on the Chrome Web Store (~17:08 Dublin, ~15.5h after submission)
+- RangerHQ Radio v1.0.0 stability milestone went LIVE on WordPress.org (~21:51 Dublin)
+- David received a PhD-prep signal from his Research in Computing lecturer at NCI Dublin
+
+A solid day.
 
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