feat: add 2-tier Greptile reply system with escalation detection

Add reply templates (Tier 1 friendly, Tier 2 firm), explicit escalation
detection algorithm, and severity re-ranking guidance to greptile-triage.md.

review/greptile-triage.md

@@ -93,6 +93,92 @@ gh api repos/$REPO/issues/$PR_NUMBER/comments \
 
 ---
 
+## Reply Templates
+
+Use these templates for every Greptile reply. Always include concrete evidence — never post vague replies.
+
+### Tier 1 (First response) — Friendly, evidence-included
+
+**For FIXES (user chose to fix the issue):**
+
+```
+**Fixed** in `<commit-sha>`.
+
+\`\`\`diff
+- <old problematic line(s)>
++ <new fixed line(s)>
+\`\`\`
+
+**Why:** <1-sentence explanation of what was wrong and how the fix addresses it>
+```
+
+**For ALREADY FIXED (issue addressed in a prior commit on the branch):**
+
+```
+**Already fixed** in `<commit-sha>`.
+
+**What was done:** <1-2 sentences describing how the existing commit addresses this issue>
+```
+
+**For FALSE POSITIVES (the comment is incorrect):**
+
+```
+**Not a bug.** <1 sentence directly stating why this is incorrect>
+
+**Evidence:**
+- <specific code reference showing the pattern is safe/correct>
+- <e.g., "The nil check is handled by `ActiveRecord::FinderMethods#find` which raises RecordNotFound, not nil">
+
+**Suggested re-rank:** This appears to be a `<style|noise|misread>` issue, not a `<what Greptile called it>`. Consider lowering severity.
+```
+
+### Tier 2 (Greptile re-flags after prior reply) — Firm, overwhelming evidence
+
+Use Tier 2 when escalation detection (below) identifies a prior GStack reply on the same thread. Include maximum evidence to close the discussion.
+
+```
+**This has been reviewed and confirmed as [intentional/already-fixed/not-a-bug].**
+
+\`\`\`diff
+<full relevant diff showing the change or safe pattern>
+\`\`\`
+
+**Evidence chain:**
+1. <file:line permalink showing the safe pattern or fix>
+2. <commit SHA where it was addressed, if applicable>
+3. <architecture rationale or design decision, if applicable>
+
+**Suggested re-rank:** Please recalibrate — this is a `<actual category>` issue, not `<claimed category>`. [Link to specific file change permalink if helpful]
+```
+
+---
+
+## Escalation Detection
+
+Before composing a reply, check if a prior GStack reply already exists on this comment thread:
+
+1. **For line-level comments:** Fetch replies via `gh api repos/$REPO/pulls/$PR_NUMBER/comments/$COMMENT_ID/replies`. Check if any reply body contains GStack markers: `**Fixed**`, `**Not a bug.**`, `**Already fixed**`.
+
+2. **For top-level comments:** Scan the fetched issue comments for replies posted after the Greptile comment that contain GStack markers.
+
+3. **If a prior GStack reply exists AND Greptile posted again on the same file+category:** Use Tier 2 (firm) templates.
+
+4. **If no prior GStack reply exists:** Use Tier 1 (friendly) templates.
+
+If escalation detection fails (API error, ambiguous thread): default to Tier 1. Never escalate on ambiguity.
+
+---
+
+## Severity Assessment & Re-ranking
+
+When classifying comments, also assess whether Greptile's implied severity matches reality:
+
+- If Greptile flags something as a **security/correctness/race-condition** issue but it's actually a **style/performance** nit: include `**Suggested re-rank:**` in the reply requesting the category be corrected.
+- If Greptile flags a low-severity style issue as if it were critical: push back in the reply.
+- Always be specific about why the re-ranking is warranted — cite code and line numbers, not opinions.
+
+---
+
 ## History File Writes
 
 Before writing, ensure both directories exist: