feat: specialist suite — configurable + custom review lenses (one consolidated comment)

Replace the single generic review with a suite of focused specialists, each its
own review+recheck pass, merged into ONE comment (a collapsible section per lens,
led by the worst verdict; the optional `improvements` lens never escalates it).

- cmd/gadfly/specialists.go: built-in lenses + default suite (security, correctness,
  maintainability, performance, error-handling) + opt-in (tests, docs, conventions,
  improvements). Selection via GADFLY_SPECIALISTS (csv/"all"); custom defs via
  GADFLY_SPECIALIST_<NAME> env and a repo .gadfly.yml (specialists + define).
  Precedence: built-ins < file < env. Unknown names error but don't sink the run.
- cmd/gadfly/consolidate.go: verdict parse + one-comment render.
- main.go: loop specialists; per-lens failure is an inline notice, never fatal.
  Default timeout bumped to 600s (suite runs sequentially).
- base system prompt trimmed to persona+tools+discipline+output; lens-specific
  focus is appended per specialist (semantic re-derivation discipline kept in base).
- entrypoint default models -> single model (suite already gives breadth; cost ~=
  specialists × models × 2). Adds gopkg.in/yaml.v3.
- docs/examples: README "Specialists" section, examples/.gadfly.yml, stub var,
  CLAUDE.md architecture/config. Dynamic `auto` selection is the planned next step.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -29,11 +29,13 @@ verifies each one against the actual code, and posts its findings as a comment.
 
 ```
 cmd/gadfly/            the reviewer binary — pure producer of review markdown (stdout)
-  main.go              agent orchestration: review pass + adversarial recheck pass, budgets
+  main.go              orchestration: loop specialists, each a review pass + adversarial recheck
+  specialists.go       specialist lenses: built-ins, default suite, env + .gadfly.yml resolution
+  consolidate.go       verdict parsing + one-comment consolidation (a section per specialist)
   model.go             provider/model resolution (majordomo.Parse) + env endpoint aliases
   tools.go             the 5 read-only repo tools (read_file/list_dir/grep/find_files/get_diff)
   recheck.go           second-pass verification prompt + verdict recompute
-  *_test.go            sandbox, recheck, wrap-up, and spec/endpoint-parse unit tests
+  *_test.go            sandbox, recheck, wrap-up, spec/endpoint-parse, specialist-resolution tests
 scripts/run.sh         fetch PR diff+meta, run the binary, upsert ONE labeled PR comment
 scripts/system-prompt.txt   the reviewer persona + verification discipline (generic, not repo-specific)
 entrypoint.sh          container brains: trigger gating, PR clone, model loop (the logic that
@@ -78,10 +80,19 @@ GADFLY_SYSTEM_FILE=scripts/system-prompt.txt ./gadfly
 
 ## Configuration
 
-The full env reference lives in the **README** (`Models & providers` + `Configuration`).
-Provider selection: `GADFLY_PROVIDER` (default `ollama-cloud`), `GADFLY_MODEL`/`GADFLY_MODELS`,
-`GADFLY_BASE_URL`, `GADFLY_API_KEY`. Named endpoint aliases via `GADFLY_ENDPOINT_<NAME>` /
-`GADFLY_ALIAS_<NAME>` (http-capable) and majordomo `LLM_*` DSNs (HTTPS-only).
+The full env reference lives in the **README** (`Specialists`, `Models & providers`,
+`Configuration`). Provider selection: `GADFLY_PROVIDER` (default `ollama-cloud`),
+`GADFLY_MODEL`/`GADFLY_MODELS`, `GADFLY_BASE_URL`, `GADFLY_API_KEY`. Named endpoint aliases via
+`GADFLY_ENDPOINT_<NAME>` / `GADFLY_ALIAS_<NAME>` (http-capable) and majordomo `LLM_*` DSNs
+(HTTPS-only).
+
+**Specialists (the swarm):** the reviewer runs a suite of focused lenses, one consolidated
+comment with a section each. Default suite = security/correctness/maintainability/performance/
+error-handling; opt-in built-ins = tests/docs/conventions/improvements. Select via
+`GADFLY_SPECIALISTS` (csv or `all`); define/override via `GADFLY_SPECIALIST_<NAME>` env or a repo
+`.gadfly.yml` (`specialists:` + `define:`). See `cmd/gadfly/specialists.go`. Cost ≈
+specialists × models × 2 passes — keep the default model count low (entrypoint defaults to one).
+Dynamic `auto` selection (a cheap model picks lenses per-diff) is the planned next step.
 
 **Tested vs untested:** only the Ollama paths (local + OpenAI-compatible pointed at Ollama)
 are actually exercised. OpenAI/Anthropic/Google come from majordomo's abstraction and are