docs: 1.0 documentation restructure

Split root CLAUDE.md into 19 per-directory files scoped to their source area.
Roll v0 history into docs/ARCHIVE.md; retire CONTEXT.md, CONTEXT-ARCHIVE.md,
PLAN.md, COMPLETED.md. Move plan docs under docs/. Rescue 9 live deferrals
into docs/TODO.md.

src/core/reclaim/CLAUDE.md

@@ -0,0 +1,41 @@
+# src/core/reclaim — pure prune orphan computation
+
+## Scope
+
+Houses the safety-critical "which files are orphans" decision for the file-lifecycle
+(prune) pillar — filesystem-free, unit-tested before any I/O exists. The filesystem
+enumeration and the actual deletion live in `shell/persist` (`prune_fs`), not here.
+
+## Invariants
+
+- **The load-bearing rule: remove creates orphans; prune reclaims them.**
+  Sample-remove and delete-bank drop index entries and may leave a file referenced
+  by nothing. Prune is the single path that turns such an orphan back into free
+  disk space. No other operation deletes a file; prune deletes only files that no
+  index references.
+- Prune reuses the shape Design View already shipped (`view_mode_model`'s
+  `reconcile(liveGuids)`): prune reconciles files on disk against referenced files
+  (the union of every bank's index) and returns the orphan set to delete — same
+  pure pattern, one level down (files instead of GUIDs).
+- Referenced-set is the union across ALL banks, pool included: a file is an orphan
+  iff no bank in the book references it. This is the safety-critical computation —
+  the prune null test is *prune never deletes a file that any index references.*
+- Orphan attribution is an owned-file manifest (fork R-D): the book tracks the set
+  of files it has created; prune reclaims `(owned ∩ on-disk) − referenced`. This
+  rejects folder-sweep (which would delete hand-dropped files).
+- **Prune null test:** a prune of a folder whose every file is referenced by some
+  bank deletes nothing; a prune deletes exactly the `present − referenced` orphan
+  set and nothing else.
+- Never a referenced file; never a non-bank file — the union-across-all-banks rule
+  protects referenced files; the ownership-attribution rule (fork R-D) protects
+  hand-dropped files.
+
+## Modules
+
+- `prune_reconcile` — pure prune core: `pruneOrphans(present, referenced, owned)` computes `(owned ∩ present) − referenced`; the safety-critical "which files are orphans" decision, filesystem-free and hard-tested before any I/O exists. Gains `mergeReferenced(bankRefs, liveInstanceHeldPaths)` (pS-usage) — unions live instance holds into the prune referenced-set so the pure orphan computation includes them.
+
+## Gotchas
+
+- Dry-run/confirm UX, trash-preferred deletion mechanics (fork R-C), and the
+  manual-trigger guardrail (fork R-E) are deletion-*mechanics* concerns, not
+  orphan-*computation* ones — they live in `shell/persist`, not here.