docs: add feature ideas catalog, time-decay scoring plan, and timeline issue doc

Ideas catalog (docs/ideas/): 25 feature concept documents covering future
lore capabilities including bottleneck detection, churn analysis, expert
scoring, collaboration patterns, milestone risk, knowledge silos, and more.
Each doc includes motivation, implementation sketch, data requirements, and
dependencies on existing infrastructure. README.md provides an overview and
SYSTEM-PROPOSAL.md presents the unified analytics vision.

Plans (plans/): Time-decay expert scoring design with four rounds of review
feedback exploring decay functions, scoring algebra, and integration points
with the existing who-expert pipeline.

Issue doc (docs/issues/001): Documents the timeline pipeline bug where
EntityRef was missing project context, causing ambiguous cross-project
references during the EXPAND stage.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/ideas/unlinked.md

@@ -0,0 +1,82 @@
+# Unlinked MR Finder
+
+- **Command:** `lore unlinked [--since <date>]`
+- **Confidence:** 83%
+- **Tier:** 2
+- **Status:** proposed
+- **Effort:** low — LEFT JOIN queries
+
+## What
+
+Two reports:
+1. Merged MRs with no entity_references at all (no "closes", no "mentioned",
+   no "related") — orphan MRs with no issue traceability
+2. Closed issues with no MR reference — issues closed manually without code change
+
+## Why
+
+Process compliance metric. Unlinked MRs mean lost traceability — you can't trace
+a code change back to a requirement. Manually closed issues might mean work was done
+outside the tracked process, or issues were closed prematurely.
+
+## Data Required
+
+All exists today:
+- `merge_requests` (state, merged_at)
+- `issues` (state, closed/updated_at)
+- `entity_references` (for join/anti-join)
+
+## Implementation Sketch
+
+```sql
+-- Orphan merged MRs (no references at all)
+SELECT mr.iid, mr.title, mr.author_username, mr.merged_at,
+       p.path_with_namespace
+FROM merge_requests mr
+JOIN projects p ON mr.project_id = p.id
+LEFT JOIN entity_references er
+    ON er.source_entity_type = 'merge_request' AND er.source_entity_id = mr.id
+WHERE mr.state = 'merged'
+  AND mr.merged_at >= ?1
+  AND er.id IS NULL
+ORDER BY mr.merged_at DESC;
+
+-- Closed issues with no MR reference
+SELECT i.iid, i.title, i.author_username, i.updated_at,
+       p.path_with_namespace
+FROM issues i
+JOIN projects p ON i.project_id = p.id
+LEFT JOIN entity_references er
+    ON er.target_entity_type = 'issue' AND er.target_entity_id = i.id
+    AND er.source_entity_type = 'merge_request'
+WHERE i.state = 'closed'
+  AND i.updated_at >= ?1
+  AND er.id IS NULL
+ORDER BY i.updated_at DESC;
+```
+
+## Human Output
+
+```
+Unlinked MRs (merged with no issue reference, last 30 days)
+
+  !245  Fix typo in README              (alice, merged 2d ago)
+  !239  Update CI pipeline              (bob, merged 1w ago)
+  !236  Bump dependency versions         (charlie, merged 2w ago)
+
+Orphan Closed Issues (closed without any MR, last 30 days)
+
+  #92   Update documentation for v2      (closed by dave, 3d ago)
+  #88   Investigate memory usage          (closed by eve, 2w ago)
+```
+
+## Downsides
+
+- Some MRs legitimately don't reference issues (chores, CI fixes, dependency bumps)
+- Some issues are legitimately closed without code (questions, duplicates, won't-fix)
+- Noise level depends on team discipline
+
+## Extensions
+
+- `lore unlinked --ignore-labels "chore,ci"` — filter out expected orphans
+- Compliance score: % of MRs with issue links over time (trend metric)