[tommasobolis]

Part of #1447

#1447 is split across four PRs. #1510 carries Closes #1447 and the full item table, so merge it last:

• docs: ledger recount, key-header row and review wording sweep (#1447) #1495: docs and ledger
• chore(cli,conformance): review hygiene sweep (#1447) #1510: CLI, simulator and conformance
• this PR: core, registry and tools docstrings, plus two small fixes
• the ADK bridged classes (branch chore/1447-adk-bridged-classes, not yet opened)

Summary

• Non-finite reset headers (fix): parse_retry_after() and retry_after() return None for a value that parses as a float but isn't finite (inf, -inf, nan, 1e400), on both Retry-After and the x-token-reset/x-ratelimit-reset fallback. Before, Retry-After: nan reached the transport's retry sleep as NaN, and time.sleep/asyncio.sleep both reject that with ValueError. inf was capped at the 30 s ceiling. Both now fall through to the jittered backoff, as an HTTP-date value already did.
• Window.fraction_used (fix): remaining is clamped into [0, limit] before the division, so a header too large for a float can't overflow it. The result is unchanged for every in-range value.
• ADR citations: the UngovernedMcpServer / governance-default citations in session.py, mcp.py, discovery.py, publication.py, models.py and donkey.py now cite ADR 0017, which superseded ADR 0013 (tools: decide how discover() and binding treat MCP servers the gateway does not front #1150). donkey.py keeps one "ADR 0013, rules kept by ADR 0017" where the history matters.
• session.py: removed the dead _check_approvals(), since describe() already refuses a require_approval() name that matches no tool. The _bind_tool docstring says so. Its vulture entry is gone, and the two tests that called it now await tools.describe().
• Discovery caching docstrings: resolve(), live_tools() and agent_card() no longer say "no cache". Nothing is cached in discovery itself, but the registry's lookups are, for registry_cache_ttl_s, and refresh() drops them.
• PublicationAssetType: the docstring now covers what Exchange records for mcp and agent, that a2a-agent isn't an Exchange type, and that api means REST/HTTP/SOAP.
• ExchangeRegistry.warm() / search(governed=) wording: these reads are answered (feat(tools): donkey.tools.warm() to pre-fill the discovery cache #1324). What isn't built is the environment-wide governed-state index, and donkey.tools.warm() pre-fills discovery instead. API Manager has no bulk policy read (§6, Verify whether applied policies can be fetched in bulk per environment #54). The _verify.blocked guard stays, because acceptance group 5 asserts it.
• ConfigWarning: the docstring lists every case that raises it: a misplaced config entry, an env switch that relaxes a check, a non-loopback serve() host, and a wait_for_gateway_approval() over 2 minutes. It's kept to two lines so core/errors.py stays within its 1030-line budget (test_oversized_core_modules_only_shrink).

Test plan

• nox -s typecheck-and-lint test-3.11 new-dependencies commit-identities (passed, after rebasing on e7859253)
• New tests:
  • test_errors.py: inf, -inf, nan and 1e400 on retry-after and on x-token-reset all give retry_after is None, and parse_retry_after() returns None for each.
  • test_budget.py::test_fraction_used_clamps_before_it_divides
• test_toolset_approval.py: the two former _check_approvals() tests run through describe(). The rebase on feat(hitl)!: settle the Approvals API: per-client registry, typed errors (#1423) #1497 kept its registry fixture.
• nox (every session): not run locally; CI runs it
• python scripts/verify_frameworks.py: n/a, no adapters or extras changed

ADR needed?

• No: this PR changes none of those.

Acceptance-harness impact

None. The group 5 warm() test asserts only that it is blocked, which is unchanged, and no acceptance test matches the reworded docstrings or blocked text.

Migration note

TokenBudgetExceeded.retry_after, RequestRateLimitExceeded.retry_after and GatewayApprovalPending.retry_after are None, not inf/nan, when the gateway sends a non-finite reset. Code that already handles None needs no change. The private ToolSet._check_approvals() is removed; describe() does the same check.

Post-deploy steps

None.