docs(adr): compress to 10 records in the domain-modeling format

[lesnik512]

Rewrites docs/adr/ from 17 records (~4,800 words) to 10 (~970 words). Each record is now a title plus one paragraph, in the domain-modeling skill's native shape; the Decision / rationale / Revisit trigger sections are gone. Where a revisit trigger was the real boundary of the decision (0013's "second backend", 0016's "second protocol") it is folded into the paragraph; the speculative ones are dropped.

Evaluation

Each record was tested against the skill's three criteria: hard to reverse, surprising without context, the result of a real trade-off.

ADR	Outcome	Why
0001 single-pass decoders	dropped	Private implementation choice. Also contradicted docs/decoders.md, which says single-pass is a performance choice for the built-ins and not a protocol obligation. The docs are right.
0002 no OTel middleware	kept	Recurring proposal, explicit no.
0003 no sync Timeout + 0009 no unasync	merged into 0003	One parity decision; 0003 was its named exception.
0004 4xx is a success	kept	The deviation the breaker is built on.
0005 time-based window	kept, absorbs #118	Same scope list; now also records the manual-control decline promised when #118 was closed.
0006 decoders frozen + 0014 broad claims	merged into 0006	0014 already cited 0006 for the same property. One dispatch decision.
0007 *_with_response + 0008 no pagination helper	merged into 0007	0008 is "the pagination primitive is send_with_response". Same surface.
0010 decide raises	dropped	Private and reversible; the _RetryPolicy class docstring already states the chaining reason.
0011 no root __reduce__	dropped	Private; the citing docstring in tests/test_errors.py now carries the reason itself.
0012 no generated reference	kept	Recurring suggestion.
0013 httpx2 is public surface	kept	Cut the module-count history.
0015 cap counts decoded bytes	kept
0016 stream bypasses chain	kept
0017 shared logic is a function	dropped	Placement rule; moved as one sentence into the _internal/ bullet in AGENTS.md.

Mechanics

• The survivors are renumbered 0001–0010 in their original order (second commit). Every reference was swept: the one intra-ADR link (0010 → 0009), the two full-path citations in tests/test_client_parity.py, the directory link in docs/index.md, and the closing comment on CircuitBreaker.force_open() / force_closed() — manual control #118 (edited to the new paths). No page, test, or sibling repo links a dropped or old number.
• tests/test_client_parity.py cited 0009 and 0003 in the short docs/adr/NNNN form, which tests/test_adr_citations.py does not match. Both now use the full path so a rename is caught.
• Checked: pytest (817 passed), ruff, eof-fixer, and lychee --offline over the touched Markdown.

Closes the ADR follow-up from #118.