Broaden Definition of Done testing rule beyond core

Require unit tests for non-trivial logic project-wide (db query/filter
logic, non-passthrough server::services code), not just core's pure
functions, per feedback that the original scope was too narrow. Thin
passthrough wrappers stay exempt, and genuinely DB/network-bound cases
must be called out explicitly rather than silently skipped.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PqTJmazHBQK878vjQ4JnnF

DEFINITION_OF_DONE.md

@@ -24,9 +24,16 @@ A change is done when all of the following hold, not just when it compiles.
 
 ## Testing
 
-- New logic in `core` (scoring, affinity math) ships with unit tests —
-  that crate is the one place pure functions make this cheap, and it's
-  already the pattern (`crates/core/src/affinity.rs`).
+- All non-trivial logic ships with unit tests wherever practical — not
+  just `core`'s pure functions (scoring, affinity math — the existing
+  pattern in `crates/core/src/affinity.rs`), but query/filter logic in
+  `db` and non-passthrough logic in `web`'s `server::services`. "Non-trivial"
+  excludes thin wrappers (a `#[server]` fn or service function that's just
+  `db.some_query(args).await?` with no branching of its own) and glue code
+  whose only failure mode is a compiler error.
+- When a DB/network dependency makes a case genuinely impractical to unit
+  test (e.g. a Diesel query's SQL correctness), say so in the PR rather
+  than silently skipping it — that's a real gap to track, not a pass.
 - Test rationale goes in a `///` doc comment above `#[test] fn`, not
   inline in the body.
 - A bug fix includes a regression test that fails on the old code.