Add project planning docs and repo scaffolding

Vision, requirements, tech stack, and phased roadmap for the space
survival game, plus Unreal-appropriate .gitignore/.gitattributes
and Git LFS setup.

docs/01_VISION.md

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+# Vision
+
+## Elevator pitch
+A multiplayer space survival game: crew a ship you build and maintain, warp across
+a galaxy of star systems, land on planets to explore and gather resources, and build
+persistent bases — both a space station and planetary outposts — as a shared base of
+operations with other players.
+
+## Reference pillars
+Three games anchor the scope. Each contributes a pillar; none should be copied wholesale.
+
+| Pillar | Reference | What we're taking |
+|---|---|---|
+| Modular ship construction & survival systems | Space Engineers / Empyrion | Grid-based building, power/thrust/hull as real systems you maintain, not cosmetic |
+| Procedural galaxy & planet landing | No Man's Sky | Seed-based generation, seamless-feeling landing, exploration-driven discovery |
+| Galaxy-scale travel | Elite Dangerous | Star map, jump/warp travel between systems, a galaxy big enough to feel unbounded |
+
+## Scope reality check
+
+Read this before getting attached to any specific milestone order.
+
+**Persistent shared-world multiplayer**, **full grid-based ship construction**, and
+**seamless procedural planets** are each, individually, the kind of feature a funded
+studio spends 1-3+ years getting right. Combined, and solo, this is a multi-year project
+even at hobbyist pace. That's not a reason not to build it — it's a reason to be
+deliberate about sequencing:
+
+1. **Architect for the full vision, build the small vision first.** Every system below
+   is designed so it *can* scale to persistent multiplayer and a full galaxy, but the
+   early phases run single-player or session-based, with one hand-built system and one
+   or two planets. See [04_ROADMAP.md](04_ROADMAP.md).
+2. **Cut scope at the hardest problems on purpose, not by accident.** The two hardest
+   technical problems here are (a) truly seamless space-to-planet-surface transitions,
+   and (b) a persistent world server that doesn't require you to run a 24/7 fleet alone.
+   The tech stack doc calls out the pragmatic version of each (instanced landing zones,
+   system-sharded servers) so you have something shippable, with a documented path to
+   the more ambitious version later.
+3. **Revisit ambition at each phase boundary.** It is completely reasonable to decide,
+   after Phase 3 or 4, that a session-based co-op game (players host, invite friends,
+   world doesn't need to persist on your infrastructure) is the right final scope rather
+   than a persistent MMO. That decision gets easier once you can see the game running.
+
+## Core pillars (functional)
+- **Fly & fight** a ship across open space in a galaxy of star systems.
+- **Build & maintain** that ship from modular components with real systems (power,
+  thrust, life support, hull integrity) that degrade and require upkeep.
+- **Warp** between star systems via a galaxy map.
+- **Land & explore** planets on foot (or surface vehicle), gather resources, encounter
+  hazards.
+- **Build bases** — a space station as a persistent home base, and planetary outposts —
+  that you and other players can return to, expand, and defend.
+- **Play together** — multiple players sharing ships, stations, and eventually a
+  persistent galaxy.