README update

Documentation pass over the README and supporting docs, incorporating the
Aug 19 review with Parathan.

README:
- Dark/light banner and Discord/Keygraph buttons via <picture>
- Add a Common Questions section at the bottom of the page
- State one consistent position on model support and provider breadth
- Name the OpenAI Responses API alongside Chat Completions
- Frame local and self-hosted models as technically supported but not
  recommended, since capability varies once the harness opens every
  provider and model
- Describe SARIF as machine-readable output rather than a CI feature

Docs:
- ai-providers: drop the Claude-preference claim; explain that capability
  varies and the model should be evaluated against your own targets
- configuration: correct rating semantics stale since v2.2.0, since
  severity is now recorded in both exploitative and analysis-only runs
- safety: reframe the model-support caveat in the same terms
- worker: correct the stale rationale on the SARIF analysis-mode gate

CI/CD documentation is intentionally omitted until the GitHub Marketplace
action lands, so the README does not ship a hand-rolled npx wrapper that
is about to be replaced.

llms.txt and llms-full.txt regenerated from source, with one deliberate
exception: the "Is Shannon free?" and "Is Shannon free for startups and
nonprofits?" questions are kept in the llms-full.txt copy of the README
but not in the README itself. That section exists for agents, so a naive
regeneration of llms-full.txt would drop them; re-add them if you rebuild
the file from source.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/configuration.md

@@ -106,12 +106,12 @@ rules:
 
 | Key | Effect |
 | --- | --- |
-| `min_severity` | Drops findings rated below this severity. Applies only when `exploit` is `"true"`. |
+| `min_severity` | Drops findings rated below this severity. Applies in both exploitative and analysis-only runs. |
 | `min_confidence` | Drops findings rated below this confidence. Applies only when `exploit` is `"false"`. |
 | `guidance` | Free-text instruction to the report agent, such as which topics to exclude. |
 | `sarif` | Emits a SARIF 2.1.0 log alongside the Markdown report. Requires `exploit: "true"`. |
 
-A finding carries one rating or the other, never both: an exploited finding is rated by severity, an analysis-only finding by confidence. Setting the threshold that does not apply to the run is ignored, and Shannon logs a warning naming the one to use instead.
+Every finding carries a severity, but it does not mean the same thing in each mode: an exploitative run measures severity from what the exploit demonstrated, while an analysis-only run assesses it from the class of flaw and the impact it would have. An analysis-only finding carries a confidence rating alongside its severity, since nothing was proven. Setting `min_confidence` on an exploitative run is ignored, and Shannon logs a warning naming the threshold to use instead.
 
 ### SARIF Output
 
@@ -125,7 +125,7 @@ report:
 
 Each finding becomes one SARIF result, filed under a rule per vulnerability class (`shannon/injection`, `shannon/xss`, `shannon/auth`, `shannon/authz`, `shannon/ssrf`) and tagged with its OWASP Top Ten 2025 category. Results are anchored to the code location the analysis phase recorded, falling back to the HTTP entry point when the finding names no file. Severity maps onto SARIF's three levels: `critical` and `high` become `error`, `medium` becomes `warning`, everything else becomes `note`.
 
-The log is written only for exploitative runs. An analysis-only run rates findings by confidence and produces no severity, so there is nothing to populate `level` with; `sarif` is ignored when `exploit` is `"false"`.
+The log is written only for exploitative runs. `sarif` is ignored when `exploit` is `"false"`.
 
 Supported rule types include `url_path`, `subdomain`, `domain`, `method`, `header`, `parameter`, and `code_path`.