docs(adr): protocol + scope decisions 0009-0013 (closes #16, #30, #69, #146, #155)

[ELares]

Five scope decisions: the compatibility contract, transaction surface, clustering posture, scale-out SLO, and advisor posture.

What

• 0009 ([DECISION]: Define and publish the IronCache compatibility tiering (Tier 0-4) #16) Tier 0-4 compatibility map; behavioral equivalence vs pinned Valkey; Lua/Functions/Streams = Tier 4.
• 0010 ([DECISION]: Transaction and scripting surface scope #30) MULTI/EXEC/DISCARD/WATCH (no-rollback) on VLL; single-shard lock-free; Lua a non-goal -> native atomic ops ([RESEARCH]: Native atomic-op set covering common scripting use cases without a Lua VM #23).
• 0011 ([DECISION]: Single-node-first roadmap with slot-ready storage layout #69) single-node-first, slot-ready per-slot shards = per-core exec units.
• 0012 ([DECISION]: Headline scale-out targets (max nodes, slots-per-node working range, rebalance-time and failover-time budgets) #146) scale-out targets: ~4096 nodes via SWIM+Raft past the ~1000 gossip ceiling; rebalance + failover budgets (Scalable analog of [DECISION]: Headline metrics are throughput-per-core and memory-at-fixed-hit-ratio #7).
• 0013 ([DECISION]: Advisor default posture (ship shadow/off by default; engine fully correct and fast with the advisor disabled) #155) advisor off by default, shadow when enabled, active tuning opt-in only.

Review focus

• Each Decision matches its issue's chosen option; behavioral-equivalence vs bit-identical is correctly framed (invariant 5).
• ADR-0012's numbers are framed as targets (not guarantees), gated on [DESIGN]: Jepsen + Elle test plan for clustering/replication #99/cluster benches; the >1000-node rationale (SWIM O(1) + Raft) is sound.
• Citations exist + support the facts; INDEX lists 0009-0013; no em/en dashes.

Closes #16. Closes #30. Closes #69. Closes #146. Closes #155. Part of M0: Vision and Scope.