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/review-coverage.md

@@ -0,0 +1,78 @@
+# DiffNote Coverage Map
+
+- **Command:** `lore review-coverage <mr-iid>`
+- **Confidence:** 75%
+- **Tier:** 3
+- **Status:** proposed
+- **Effort:** medium — join DiffNote positions with mr_file_changes
+
+## What
+
+For a specific MR, show which files received review comments (DiffNotes) vs. which
+files were changed but received no review attention. Highlights blind spots in code
+review.
+
+## Why
+
+Large MRs often have files that get reviewed thoroughly and files that slip through
+with no comments. This makes the review coverage visible so teams can decide if
+un-reviewed files need a second look.
+
+## Data Required
+
+All exists today:
+- `mr_file_changes` (new_path per MR)
+- `notes` (position_new_path, note_type='DiffNote', discussion_id)
+- `discussions` (merge_request_id)
+
+## Implementation Sketch
+
+```sql
+SELECT
+    mfc.new_path,
+    mfc.change_type,
+    COUNT(DISTINCT n.id) as review_comments,
+    COUNT(DISTINCT d.id) as review_threads,
+    CASE WHEN COUNT(n.id) = 0 THEN 'NOT REVIEWED' ELSE 'REVIEWED' END as status
+FROM mr_file_changes mfc
+LEFT JOIN notes n ON n.position_new_path = mfc.new_path
+    AND n.note_type = 'DiffNote'
+    AND n.is_system = 0
+LEFT JOIN discussions d ON n.discussion_id = d.id
+    AND d.merge_request_id = mfc.merge_request_id
+WHERE mfc.merge_request_id = ?1
+GROUP BY mfc.new_path
+ORDER BY review_comments DESC;
+```
+
+## Human Output
+
+```
+Review Coverage for !234 — Refactor auth middleware
+
+  REVIEWED (5 files, 23 comments)
+    src/auth/middleware.rs        12 comments, 4 threads
+    src/auth/jwt.rs               6 comments, 2 threads
+    src/auth/session.rs           3 comments, 1 thread
+    tests/auth/middleware_test.rs  1 comment, 1 thread
+    src/auth/mod.rs               1 comment, 1 thread
+
+  NOT REVIEWED (3 files)
+    src/auth/types.rs             modified    [no review comments]
+    src/api/routes.rs             modified    [no review comments]
+    Cargo.toml                    modified    [no review comments]
+
+  Coverage: 5/8 files (62.5%)
+```
+
+## Downsides
+
+- Reviewers may have reviewed a file without leaving comments (approval by silence)
+- position_new_path matching may not cover all DiffNote position formats
+- Config files (Cargo.toml) not being reviewed is usually fine
+
+## Extensions
+
+- `lore review-coverage --all --since 30d` — aggregate coverage across all MRs
+- Per-reviewer breakdown: which reviewers cover which files?
+- Coverage heatmap: files that consistently escape review across multiple MRs