Docs: note SL-5 code portion (telegraph + retry/quit) shipped early

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Docs/Vault/06_Roadmap/Backlog.md

@@ -50,6 +50,7 @@ Last decluttered 2026-06-08 (removed all shipped `[x]` items; their context is p
 - **Deps:** SL-1 (locked arena). Cut perimeter props first if it slips; keep darkening + emissive.
 
 ### SL-5 — Final Siege & Ending tuning `Jun 24-26` · risk MED
+> **Code portion STARTED early 2026-06-13** (on the back of SL-3): the HUD **final-siege telegraph** (distinct "FINAL SIEGE INCOMING" / "HOLD THE ENGINE", derived from the replicated `Charge>=Target`) + the **retry/quit-on-banner overlay** (PLAY AGAIN = fresh Single run via `WorldLauncher.StartSession`; QUIT TO MENU = teardown; cursor kept visible via `AimReticleSystem`'s run-over exception) are SHIPPED + 342/342 green. **Remaining = tuning/playtest only:** `FinalSiegeMultiplier` values (2.0/2.5/3.0), the richer telegraph (Engine hum/sky shift), Victory/Loss banner feel, 3+ runs at 5–8 min, co-op desync check — and a Play **click-test** of the banner buttons. See [[2026-06-13_SL3_END2_Final_Siege_Win_Lose]].
 - **Goal:** make the final siege feel climactic and the run a clear three-act (prep → conflict → climax/resolution); lock end-game messaging.
 - **Tasks:** tune `FinalSiegeMultiplier` (test 2.0/2.5/3.0; final peak ≥30 % over normal) · add a final-siege **telegraph** (Engine hum/sky shift/HUD "FINAL SIEGE INCOMING", ≥3–5 s warning) · validate Victory banner only on final-`DefendCleared`, Loss banner distinct from mid-run overrun · autosave the victory/loss checkpoint + clean continue/retry/quit flow (no soft-lock) · clock 3+ runs at 5–8 min · co-op: both clients see the same outcome, no desync.
 - **Fun-gate:** a new team unanimously reads the final siege as *different*, preps for it, and reads winning as winning (not "another siege cleared"); run duration 5–8 min ±1 across 3+ playthroughs.