feat(canon): add inter-repo communication standard with todo taxonomy

Establishes the repo boundary rule and a formal vocabulary for classifying
work items by scope:

- Task: neutral state hub data entity
- Todo: a task scoped to the current session's repo/domain
  - Internal todo: addressed within this repo by this agent
  - Ecosystem todo: work for another registered repo → state hub task [repo:<slug>]
  - Third-party todo: work for an upstream repo → contribution artifact (BR/FR/EP/UPR)

New dashboard doc: /docs/inter-repo-communication — defines the boundary rule,
the full terminology, ecosystem and third-party todo workflows, and a decision
table for classifying any piece of work found during a session.

Also:
- sbom.md: replace verbose inter-repo section with a 3-line summary + link
- observablehq.config.js: add "Inter-Repo Communication" to Reference nav
- project_claude_md.template: add "### Repo Boundary Rule" section; fix
  Workplan Convention section (removing incorrect claim that the custodian
  writes workplan files in other repos — that is the target repo's job)

Cross-repo: created state hub task [repo:railiance-bootstrap] for that repo's
agent to apply the boundary rule and workplan convention fix to its own CLAUDE.md
(task 78d43cb0, workstream 59155efb).

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

dashboard/src/docs/sbom.md

@@ -157,19 +157,12 @@ hand-rolled parsers for comprehensive coverage.
 
 ## Inter-repo task communication
 
-When the State Hub or custodian identifies a compliance gap in a registered repo,
-the task is communicated through two channels:
+When a compliance gap is identified in a registered repo, the finding is routed
+as an **ecosystem todo**: a state hub task with `[repo:<slug>]` in the title,
+created in the target domain's workstream. The target repo's session protocol
+surfaces it automatically at next session start.
 
-1. **State Hub task** — created in the relevant domain workstream with
-   `[repo:<slug>]` in the title. Visible via `get_state_summary()` at the
-   start of any domain session.
-
-2. **Workplan file** — a `workplans/<ID>-<slug>.md` file is created in the
-   target repo itself (ADR-001 convention). When you open that repo in Claude
-   Code, the session protocol surfaces it.
-
-When working in a registered repo, always run `get_state_summary()` at session
-start — the state hub surfaces pending tasks for your domain automatically.
+See the full standard: [`/docs/inter-repo-communication`](/docs/inter-repo-communication)
 
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