feat(#1825): configurable graphify graph location (graphify.graph_path) (#2013)

* feat(#1825): configurable graphify graph location (graphify.graph_path)

Add a graphify.graph_path config key (.planning/config.json) that overrides
where /gsd-graphify query|status|diff read the knowledge graph, so one curated
umbrella-level cross-repo graph can serve multiple sibling projects without N
drifting ~5 MB mirror copies. Previously the graph location was hardcoded to
<cwd>/.planning/graphs/.

- src/graphify.cts: resolveGraphLocation(cwd, planningDir) honors the key
  (resolved relative to project root; absolute paths honored via path.resolve);
  falls back to the historical .planning/graphs/graph.json when unset/blank/
  non-string (byte-identical). Wired into graphifyQuery, graphifyStatus,
  graphifyDiff (snapshot travels with the configured graph via dirname), and
  writeSnapshot. Configured-but-missing -> actionable error naming the path.
  Build stays project-scoped (skill hardcodes the cp dest); umbrella graph is
  built in the umbrella project, sub-projects only READ it.
- config-schema.manifest.json: register graphify.graph_path in validKeys.
- tests/graphify-graph-path.test.cjs: boundary matrix (unset byte-identical,
  set+present reads configured graph not default, set+missing actionable error,
  relative resolved vs project root, blank treated as unset, snapshot alongside
  configured graph, diff from configured dir, build project-scoped) +
  VALID_CONFIG_KEYS registration.
- docs: CONFIGURATION.md row, FEATURES.md REQ-GRAPH-06, CONTEXT.md module note,
  .changeset (Added).

Closes #1825

* docs(#1825): backfill changeset pr number 2013

docs/CONFIGURATION.md

@@ -708,6 +708,7 @@ gsd-tools query config-set mempalace.cross_project_tunnels true
 | `graphify.enabled` | boolean | `false` | Enable the project knowledge graph. When `true`, `/gsd-graphify` builds and queries a graph in `.planning/graphs/`. Added in v1.36 |
 | `graphify.build_timeout` | number (seconds) | `300` | Maximum seconds allowed for a `/gsd-graphify build` run before it aborts. Added in v1.36 |
 | `graphify.auto_update` | boolean | `false` | **Opt-in (issue #3347).** When `true` (and `graphify.enabled` is also `true`), the bundled PostToolUse hook `hooks/gsd-graphify-update.sh` auto-rebuilds the project knowledge graph in a detached background process after `git commit/merge/pull/rebase --continue/cherry-pick` on the default branch (`git.base_branch` override, else `main`/`master`/`trunk`). Hook returns instantly; the rebuild updates `.planning/graphs/{graph.json,graph.html,GRAPH_REPORT.md}` and writes `.planning/graphs/.last-build-status.json` (`{ts, status: "running"\|"ok"\|"failed", exit_code, duration_ms, head_at_build}`). PID-locked, CI-aware (`$CI` env suppresses), bails silently if `graphify` is not on `PATH`. Default `false` so existing behaviour is unchanged after upgrade. |
+| `graphify.graph_path` | string (path) | _unset_ | **Umbrella/multi-repo support (issue #1825).** Overrides where `/gsd-graphify query\|status\|diff` read the knowledge graph from. Set to a path (relative to the project root, or absolute) pointing at a shared umbrella-level `graph.json` so a single curated cross-repo graph serves every sub-project without N drifting mirror copies. The diff snapshot (`.last-build-snapshot.json`) travels with the configured graph (same directory); the auto-update status sidecar stays project-local. Build stays project-scoped (`.planning/graphs/`) — build the umbrella graph in the umbrella project, then point sub-projects at it. When unset, behaviour is byte-identical to the historical `.planning/graphs/graph.json`. A clear, actionable error is returned when the configured file is missing. |
 
 #### Multi-developer setup
 

docs/FEATURES.md

@@ -2626,8 +2626,9 @@ Users who run a memory / knowledge-base MCP server (for example, ExoCortex-style
 - REQ-GRAPH-03: Build runs within the configurable `graphify.build_timeout` (seconds); exceeding the timeout aborts cleanly without leaving a partial graph.
 - REQ-GRAPH-04: `graphify.cjs` falls back to `graph.links` when `graph.edges` is absent so older graph artifacts keep rendering.
 - REQ-GRAPH-05: Graphify is invoked through `gsd-tools.cjs graphify ...` command handlers.
+- REQ-GRAPH-06: The knowledge-graph location is configurable via `graphify.graph_path` (issue #1825) so one umbrella-level cross-repo graph can serve multiple sibling projects; `query`/`status`/`diff` read the configured graph (relative to project root), with a byte-identical `.planning/graphs/` default when unset.
 
-**Configuration:** `graphify.enabled`, `graphify.build_timeout`
+**Configuration:** `graphify.enabled`, `graphify.build_timeout`, `graphify.graph_path`
 **Reference files:** `commands/gsd/graphify.md`, `bin/lib/graphify.cjs`
 
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