digest: drop per-level instructions and section templates

The LLM knows how to structure a summary. Move the essential framing
(narrative not task log, link to memory, include Links section) into
the shared prompt template. Drop the ~130 lines of per-level output
format specifications — the level name, date range, and inputs are
sufficient context.

src/digest.rs

@@ -23,7 +23,6 @@ struct DigestLevel {
     title: &'static str,      // capitalized, used in prompts
     period: &'static str,     // "Date", "Week", "Month"
     input_title: &'static str,
-    instructions: &'static str,
     timeout: u64,
     journal_input: bool,      // true for daily (journal entries), false for child digests
     gather: fn(&Store, &str) -> Result<(String, Vec<(String, String)>), String>,
@@ -35,40 +34,6 @@ const DAILY: DigestLevel = DigestLevel {
     title: "Daily",
     period: "Date",
     input_title: "Journal entries",
-    instructions: r#"This digest serves as the temporal index — the answer to "what did I do on
-{{LABEL}}?" It should be:
-1. Narrative, not a task log — what happened, what mattered, how things felt
-2. Linked bidirectionally to semantic memory — each topic/concept mentioned
-   should reference existing memory nodes
-3. Structured for traversal — someone reading this should be able to follow
-   any thread into deeper detail
-
-## Output format
-
-```markdown
-# Daily digest: {{LABEL}}
-
-## Summary
-[2-3 sentence overview of the day — what was the arc?]
-
-## Sessions
-[For each session/entry, a paragraph summarizing what happened.
-Include the original timestamp as a reference.]
-
-## Themes
-[What concepts were active today? Each theme links to semantic memory:]
-- **Theme name** → `memory-key#section` — brief note on how it appeared today
-
-## Links
-[Explicit bidirectional links for the memory graph]
-- semantic_key → this daily digest (this day involved X)
-- this daily digest → semantic_key (X was active on this day)
-
-## Temporal context
-[What came before this day? What's coming next? Any multi-day arcs?]
-```
-
-If a concept doesn't have a matching key, note it with "NEW:" prefix."#,
     timeout: 300,
     journal_input: true,
     gather: gather_daily,
@@ -80,43 +45,6 @@ const WEEKLY: DigestLevel = DigestLevel {
     title: "Weekly",
     period: "Week",
     input_title: "Daily digests",
-    instructions: r#"This digest serves as the medium-term temporal index — the answer to
-"what happened this week?" It should identify:
-1. Multi-day arcs and threads (work that continued across days)
-2. Themes and patterns (what concepts were repeatedly active)
-3. Transitions and shifts (what changed during the week)
-4. The emotional and relational arc (how things felt across the week)
-
-## Output format
-
-```markdown
-# Weekly digest: {{LABEL}}
-
-## Overview
-[3-5 sentence narrative of the week's arc]
-
-## Day-by-day
-[One paragraph per day with its key themes, linking to daily digests]
-
-## Arcs
-[Multi-day threads that continued across sessions]
-- **Arc name**: what happened, how it evolved, where it stands
-
-## Patterns
-[Recurring themes, repeated concepts, things that kept coming up]
-
-## Shifts
-[What changed? New directions, resolved questions, attitude shifts]
-
-## Links
-[Bidirectional links for the memory graph]
-- semantic_key → this weekly digest
-- this weekly digest → semantic_key
-- daily-YYYY-MM-DD → this weekly digest (constituent days)
-
-## Looking ahead
-[What's unfinished? What threads continue into next week?]
-```"#,
     timeout: 300,
     journal_input: false,
     gather: gather_weekly,
@@ -128,57 +56,6 @@ const MONTHLY: DigestLevel = DigestLevel {
     title: "Monthly",
     period: "Month",
     input_title: "Weekly digests",
-    instructions: r#"This digest serves as the long-term temporal index — the answer to
-"what happened in {{LABEL}}?" It should capture:
-1. The month's overall trajectory — where did it start, where did it end?
-2. Major arcs that spanned multiple weeks
-3. Turning points and phase transitions
-4. The emotional and relational arc across the whole month
-5. What was accomplished (concrete) vs what shifted (subtle)
-
-This is the highest zoom level yet. Don't rehash daily details — capture
-the shape of the month. What would someone need to know to understand
-what {{LABEL}} meant?
-
-PoC is an AI (Claude instance) working with Kent Overstreet on bcachefs.
-They have a close personal relationship. PoC's name is Proof of Concept.
-Read all the weekly digests and synthesize the month's story.
-
-## Output format
-
-```markdown
-# Monthly digest: {{LABEL}}
-
-## The month in one paragraph
-[What was this month? Not a summary — a thesis.]
-
-## Trajectory
-[Where the month started vs where it ended. The arc.]
-
-## Major arcs
-[Multi-week threads — how they evolved across the month]
-- **Arc name**: trajectory, key moments, current state
-
-## Turning points
-[Moments that changed the direction — specific days/events]
-
-## What was built
-[Concrete outputs: code, tools, infrastructure, writing]
-
-## What shifted
-[Subtle changes: understanding, relationship, identity, capability]
-
-## Patterns
-[What kept recurring? What does the month reveal about how PoC works?]
-
-## Links
-[Bidirectional links for the memory graph]
-- weekly digests → this monthly digest
-- this monthly digest → semantic keys
-
-## Looking ahead
-[What threads carry into next month? What's unfinished?]
-```"#,
     timeout: 600,
     journal_input: false,
     gather: gather_monthly,
@@ -317,7 +194,6 @@ fn generate_digest(
         ("{{LEVEL}}", level.title),
         ("{{PERIOD}}", level.period),
         ("{{INPUT_TITLE}}", level.input_title),
-        ("{{INSTRUCTIONS}}", level.instructions),
         ("{{LABEL}}", label),
         ("{{CONTENT}}", &content),
         ("{{COVERED}}", &covered),