Remove internal repo reference; add harness-cache gitignore

CHANGELOG.md: drop "(copied from flashalpha-api)" note that referenced
the internal monorepo name.

.gitignore: add cross-ecosystem harness-cache patterns (.dotnet/,
.gocache/, .gopath/, .m2/, .review-artifacts/, .agent-tools/) so
sandbox/agent runners can't accidentally land toolchain caches in
git regardless of the package's primary language.

Author: tdobrowolski1

.gitignore

@@ -211,3 +211,11 @@ cython_debug/
 marimo/_static/
 marimo/_lsp/
 __marimo__/
+
+# Sandbox / agent / harness caches (cross-ecosystem — defensive)
+.dotnet/
+.gocache/
+.gopath/
+.m2/
+.review-artifacts/
+.agent-tools/

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## Unreleased
 
 ### Added
-- `docs/api.md` — full endpoint reference, URL-prefix table, response schemas, and sample JSON for every endpoint (copied from flashalpha-api)
+- `docs/api.md` — full endpoint reference, URL-prefix table, response schemas, and sample JSON for every endpoint
 - 17 integration regression tests (`tests/test_integration.py`) guarding against response-shape and URL-pattern regressions reported by Alpha users:
   - Nested VRP response (`vrp.z_score`, `gex_conditioned.harvest_score`, `regime.net_gex`, `directional.*`)
   - `exposure_summary` nesting (`exposures.net_gex`)