docs: refine reader digest flow public/internal rules

reader-digest-flow/references/flow.md

@@ -56,17 +56,35 @@ Typical artifacts to inspect after a successful run:
 
 ```text
 outputs/freshrss/rerun/<run-id>/candidates/openclaw-delivery-payload.json
+outputs/freshrss/rerun/<run-id>/candidates/digest-brief.json
 outputs/freshrss/rerun/<run-id>/run-report.json
 outputs/freshrss/rerun/<run-id>/extracted/item-XX.extracted.json
 ```
 
+Notes:
+
+- `digest-brief.json` is the preferred input for **public digest** generation.
+- It is a lighter public-only view and currently includes only `keep` candidates.
+- If `digest-brief.json` is missing, fall back to `openclaw-delivery-payload.json`.
+
 ### 2. Generate digest markdown
 
-Generate two output views from the same payload:
+Generate two output views from the same run, preferably in one model call:
 
 1. a **public digest** for Hugo / public readers
 2. an **internal review digest** for chat / operator workflow
 
+Input preference:
+
+- **public digest**: prefer `candidates/digest-brief.json`
+- **internal review digest**: use `candidates/openclaw-delivery-payload.json`
+
+Recommended generation pattern:
+
+- Pass the public brief and the full payload as two explicitly labeled input blocks.
+- Ask the model to return both outputs in one response.
+- Prefer a structured response shape (for example JSON with `public_digest_markdown` and `internal_review_digest_markdown`) when post-processing is needed.
+
 Write only the public digest into Hugo here:
 
 ```text
@@ -91,6 +109,13 @@ Recommended **public digest** structure:
 - `延伸阅读`
 - `信息来源`
 
+Public digest constraints:
+
+- Use only the public brief view when present.
+- Keep public wording free of internal workflow language.
+- Optimize for concise public readability with solid information density.
+- For each `今日重点` item, add one short editor-style sentence explaining why the item matters in today's digest (for example: `这篇内容更值得关注的原因在于……`).
+
 Recommended **internal review digest** structure:
 
 - `今日候选概况`
@@ -99,6 +124,14 @@ Recommended **internal review digest** structure:
 - `建议沉淀到 IMA`
 - `原始候选清单`
 
+Internal review digest constraints:
+
+- Do not show `rank` values.
+- Replace machine states with Chinese labels such as `已入选` / `待确认` / `暂不纳入`.
+- For `已入选重点`, include a fuller summary plus a short judgment paragraph.
+- For `待你确认`, include a fuller summary, reason, and recommendation.
+- Keep it readable as an operator review draft, not a raw payload dump.
+
 ### 3. Publish Hugo
 
 Publish only the public digest to Hugo.