agentdb graph k-hop: native backend ignores `relation`; SQL fallback caps depth at 3 while callers ask for 5

Found during the 2026-09-05 PR-review mission (agent `pr-review-small-repos`, verifying ruvnet/ruClip#13).

**Observed (read, not inferred):**
- `v3/@claude-flow/cli/src/mcp-tools/agentdb-tools.ts:1033-1040` (`agentdb_graph-query`, k-hop): the native graph backend path calls `getNeighbors(nodeId, depth)` with **no `relation` argument**, so a caller's `relation` filter is silently ignored on that backend.
- The SQL fallback path **caps depth at 3**, while ruClip's cycle-prevention check asks for depth 5.

**Effect:** the same k-hop query can over-reject (relation ignored → extra edges counted) or under-reach (depth 5 truncated to 3) depending on which backend is active. ruClip#13 fixed the response-shape parsing (`results: [{nodeId}]`) on the caller side; this is the remaining server-side inconsistency.

**Ask:** pass `relation` through on the native path (or document that it is unsupported and return an explicit `unsupported` field), and either lift the SQL depth cap or surface the applied depth in the response so callers can detect truncation.

Evidence: ruClip's installed `@claude-flow/cli@3.38.20` carries the same code.

🤖 Generated with [RuFlo](https://github.com/ruvnet/ruflo)

https://claude.ai/code/session_019xHM4rAH4aaShb4DTr1n6s

Start in v3/@claude-flow/cli/src/mcp-tools/agentdb-tools.ts:1033-1040 at the agentdb_graph-query k-hop entry point, and compare the native getNeighbors call with the SQL fallback. Verify relation filtering and depth behavior for callers requesting depth 5; done means both backends provide consistent, detectable behavior without silently ignoring relation or truncating depth.

Written by the indexing model from the issue text.