feat(repos): multi-machine path support via host_paths

Adds a JSONB column `host_paths` to managed_repos mapping
hostname → absolute local path. Fixes the consistency-checker
failure when the same repo lives at different paths on different
machines (e.g. /home/worsch/marki-docx on the workstation vs
/home/tegwick/marki-docx on custodiancore).

Changes:
- Migration g4b5c6d7e8f9: adds host_paths JSONB (default {})
- Model: host_paths Mapped[dict] column
- Schemas: host_paths in RepoRead; new RepoPathRegister schema
- Router: POST /repos/{slug}/paths/ — merges one host entry
- consistency_check.py: resolve_repo_path() prefers host_paths
  [hostname] over local_path; --repo-path CLI override added
- MCP: update_repo_path(slug, path, host?) tool
- Makefile: register-path target; REPO_PATH passthrough on
  check-consistency and fix-consistency targets
- TOOLS.md: documents update_repo_path

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

migrations/versions/g4b5c6d7e8f9_add_host_paths_to_repos.py

@@ -0,0 +1,38 @@
+"""add host_paths to managed_repos
+
+Revision ID: g4b5c6d7e8f9
+Revises: f3a4b5c6d7e8
+Create Date: 2026-03-16
+
+Adds a JSONB column `host_paths` to managed_repos mapping hostname → absolute
+local path. This allows the same repo to be registered at different paths on
+different machines (e.g. /home/worsch/marki-docx on the workstation and
+/home/tegwick/marki-docx on custodiancore). The consistency checker and any
+other path-resolving code prefers host_paths[current_hostname] over local_path.
+"""
+from __future__ import annotations
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = "g4b5c6d7e8f9"
+down_revision = "f3a4b5c6d7e8"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "managed_repos",
+        sa.Column(
+            "host_paths",
+            postgresql.JSONB(astext_type=sa.Text()),
+            nullable=False,
+            server_default="{}",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("managed_repos", "host_paths")