docs: REQUIREMENTS.md — OpenGL 4.3 floor, disk/RAM planning

Acer M5-481T fails Ghostty because Ivy Bridge HD 4000 tops out at
OpenGL 4.2 in Mesa; Ghostty needs 4.3 — a generation ceiling, not a
missing driver. Document that plus UEFI/x86_64, RAM, and storage floors
(Nix store generations + BTRFS snapper + hibernate swap≈RAM). Linked
from README, docs map, HARDWARE.md; #95 points here.

agent/BACKLOG.md

@@ -149,6 +149,13 @@ browser posture is explicit).
 **Machine:** Acer Aspire M5-481T only. **Dell XPS 9350 starts Ghostty fine**
 (Bernardo clarified 2026-07-15 — do not treat XPS as a Ghostty failure).
 
+**Why this hardware fails:** the Aspire is Ivy Bridge–class (**Intel HD
+4000**, ~2012). Mesa’s max for that GPU is **OpenGL 4.2**; Ghostty requires
+**4.3**. That is a **generation ceiling**, not a missing package — no
+Nomarchy or Mesa tweak can make HD 4000 report 4.3 honestly. Documented in
+`docs/REQUIREMENTS.md`. The product response is a fallback terminal (or
+probe), not “fix Intel drivers.”
+
 On the Acer, Bernardo installed **kitty** by hand (worked) and launched
 Ghostty from that shell twice — **same box, two lifecycle points, two log
 shapes**:

agent/JOURNAL.md

@@ -19,6 +19,18 @@ Template:
 
 ---
 
+## 2026-07-15 — docs/REQUIREMENTS.md (OpenGL floor + disk planning)
+- **Task:** Bernardo: why Acer lacks OpenGL 4.3; start documenting minimum
+  system requirements including storage (Nix store + snapshots).
+- **Did:** Answer is hardware generation (HD 4000 / Ivy Bridge tops at GL
+  4.2; Ghostty needs 4.3). New `docs/REQUIREMENTS.md` — UEFI/x86_64, GPU
+  table, RAM, disk floors (40/64/128 GiB) + swap≈RAM, why store+snapper grow;
+  linked from README, docs map, HARDWARE.md; #95 notes the generation ceiling.
+- **Verified:** V0 (docs only).
+- **Pending:** #95 still needs a runtime fallback; tighten disk numbers when
+  a fresh install is `df`-measured end-to-end.
+- **Next suggestion:** #123 (installer bake).
+
 ## 2026-07-15 — File install findings from Acer + XPS photos (no code)
 - **Task:** Bernardo: real installs on Acer Aspire M5-481T + Dell XPS 9350;
   photos of the install end screens and post-boot sessions. Figure out