Remove in-repo ADRs from 07-references.md (§6.2.1)

`architecture/07-references.md` §6.2.1 (TSAI Documents) lists the TSAI ADRs as informative references. Two problems:

- The list is stale — it stops at ADR 010 and is missing 011, 012, 013. Keeping it in lockstep with `decisions/` is ongoing maintenance with little payoff.
- A references section is for external/normative sources. In-repo ADRs are discoverable by browsing `decisions/` and are already linked from the spec sections that depend on them.

Proposal: drop the in-repo ADR entries from §6.2.1 rather than maintaining the list. Open question whether the `concept/` entry should go the same way.

Out of scope for #4; filing separately.

Read architecture/07-references.md §6.2.1 and inspect the entries under decisions/ to confirm which in-repo ADR links are listed. Remove the ADR references, resolve whether the concept/ entry belongs there, and verify that the section contains only the intended external or normative references.

Written by the indexing model from the issue text.