docs(phase-16): resolve decisions D1-D7; re-sequence waves bottom-up, card last

PLAN.md

@@ -245,16 +245,17 @@ The phase deferred behind the home-hero **Plays** stat card (`NowPlayingStats.ra
 
 **Architectural spine.** Plays are instrumented at **one seam** — the `StreamingAudioPlayerService` playback lifecycle (not the UI, not the HTTP/media-client layer, which fires multiple times per play via seek-beyond-buffer). A small play-session tracker opens on playback-start, advances a high-water position on the existing progress callback, and closes (classifying the §1 completion bucket) on track-switch / stop / organic-end / page-unload. Shares instrument at the **real** share surface (`SharePopover`'s Copy-link / Copy-embed actions — clipboard writes that record nothing today). Events ship **fire-and-forget via `sendBeacon`** to new `POST api/event/{play,share}` endpoints (proxied through `DeepDrftPublic`, same hop as `api/track/*`), land in an **append-only SQL event log + incremental counter rollup** in `DeepDrftData`, and the home card reads the total through the **existing** `GET api/stats/home` / `HomeStatsDto` / `IStatsDataService` path (the same single persistent-state-bridged round-trip the other two cards use). Release attribution is **resolved server-side** from the track→release join (client sends only the track key); release plays are **derived** (sum of their tracks' plays). All SQL — the FileDatabase vault is not involved.
 
-**Completion buckets (agreed thresholds).** `partial` < 30%, `complete` > 80%; the 30–80% middle band is proposed as its own `sampled` bucket so the three are exhaustive and non-overlapping (headline plays = sum of all three) — see spec §1a / decision **D1**.
+**Completion buckets (settled).** `partial` < 30%, `sampled` 30–80%, `complete` > 80% — exhaustive, non-overlapping; headline plays = sum of all three (D1 resolved). The engagement floor (D2) drops trivial skips: a listen counts only at **≥3s OR ≥5% of duration, whichever smaller**.
 
-**Sequenced as four waves.** `16.A → 16.B`, `16.A → 16.C`, `16.A → 16.D`. 16.A is the only cold-start wave.
+**Sequenced BOTTOM-UP (Daniel directive 2026-06-19): foundation first, the live card LAST.** Reverses the earlier "visible win early" framing — Daniel does not care about the live card until the whole substrate and all metrics are finished. Strict chain: `16.1 → 16.2 → 16.3 → (16.4 optional) → 16.5`. 16.1 is the only cold-start wave; 16.5 (the card) is the capstone built last.
 
-- **16.A — Play & share counters (core).** Player-service play tracker (three-bucket classification + engagement floor), share tracker in `SharePopover`, `sendBeacon` interop + `POST api/event/{play,share}` (rate-limited), `play_event`/`share_event` log + incremental `play_counter` rollup, server-side release resolution. **No `anonId` yet.** Free-floating cold-start wave.
-- **16.B — Home Plays-card payoff.** Extend `HomeStatsDto` + `GetHomeStatsAsync` with `TotalPlays` (+ a secondary line, D7); flip the third card from placeholder to live. **Depends on 16.A.** The visible win — sequence immediately after 16.A.
-- **16.C — Unique listeners (stretch / "plus").** The anonymity mechanism (recommend a client-minted random first-party `localStorage` id; alt: server-derived salted daily token; fingerprinting rejected — see §3 / **D5**): thread an `anonId` onto event payloads, count distinct server-side, expose per-target and/or as the card's secondary line. **Depends on 16.A. Explicitly lower priority** — defers indefinitely without stranding 16.A/16.B.
-- **16.D — Per-target stats surfaces.** `[speculative]` — detail-page play/share/listener display + CMS analytics views (bucket/channel splits, leaderboards). Not in the agreed scope; the event log already supports it. Build when a surface wants it.
+- **16.1 — Foundation: capture seam + transport + event log (nothing reads it yet).** Player-service play tracker (high-water mark + engagement floor), share tracker in `SharePopover` (debounced), `sendBeacon` interop + unload handler, `POST api/event/{play,share}` (proxied, rate-limited), append-only `play_event`/`share_event` log + incremental `play_counter` rollup, server-side release resolution + derived release totals. **No `anonId` yet; no card consumption.** Cold-start wave.
+- **16.2 — Completion-bucket classification + shares.** Three-bucket classification (D1) correct and exhaustive end to end (tracker → payload → log → per-bucket counter columns); share-channel split (link/embed). **Depends on 16.1.**
+- **16.3 — Unique-listener `anonId` layer (lowest-priority metric, D5).** Option A: mint/read client first-party `localStorage` id, thread `anonId` onto payloads (nullable in the log), count distinct server-side (all-time, D3). **The last metric layer** — folded into "everything finished," explicitly last-built of the substrate. **Depends on 16.1; builds on 16.2.**
+- **16.4 — Per-target / CMS stats surfaces.** `[speculative]` — `GET api/stats/{track,release}/{key}` + CMS analytics views (bucket/channel splits, leaderboards). Not committed; the event log already supports it. Off the critical path to the card; build before the capstone only if a surface wants it. **Depends on 16.1–16.3.**
+- **16.5 — Home Plays-card payoff (CAPSTONE, built LAST).** Extend `HomeStatsDto` + `GetHomeStatsAsync` with `TotalPlays` (+ secondary line = unique listeners, D7); flip `NowPlayingStats`'s third card from placeholder to live through the existing `GET api/stats/home` round-trip. **The final wave — built only once 16.1–16.3 are in place.**
 
-**Open product decisions (D1–D7, spec §10) — unresolved, awaiting Daniel.** Headline is **D5** (unique-listener anonymity mechanism). Others: D1 (middle-band bucket), D2 (engagement floor before a play counts), D3 (unique-listener window), D4 (release plays derived vs. counted), D6 (rollup strategy), D7 (card secondary line). Resolve before 16.A is decomposed; recommendations are carried in the spec.
+**Product decisions D1–D7 — RESOLVED (Daniel 2026-06-19, spec §10).** D1 (three-bucket sampled), D2 (engagement floor on, ≥3s/≥5%), D4 (release plays derived server-side), D5 (Option A — client-minted first-party `localStorage` id, metric labelled "listeners," fingerprinting rejected) resolved on explicit pick. D3 (all-time window), D6 (incremental-on-write rollup), D7 (card secondary = unique listeners) resolved-by-default — low-risk to revisit during their wave. Road-not-taken preserved in the spec.
 
 **Adjacency to deferred Identity / accounts (the un-phased backlog item above).** This phase is the deliberate **anonymous** answer to "how many plays" — it does **not** need the accounts/identity work and must not be entangled with it. If identity ever lands, per-user listening history is an additive layer above this anonymous substrate, not a replacement.