fix(foundation): Extractor.output message, make_name registry pollution, scapy engine _offmt

[JarryShaw]

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• Followed the coding style (make pylint, make mypy, make isort): ran pylint, mypy and isort on the three files. The new module scores 10.00, and no findings fall on changed lines. The findings that remain are pre-existing.
• make test passes, and a test case covers the change: see the modules below
• Added a changelog entry: N/A, added centrally after the wave

What is the purpose of your pull request?

• fix — corrects a defect

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Description of your pull request and other information

Closes #1095.

• Extractor.output now names output in its UnsupportedCall. The sibling properties (format, frame, reassembly, trace) were already correct.
• make_name now uses __output__.get(fmt), so an unknown format is no longer inserted into the defaultdict.
• The scapy engine's read_frame sets ext._offmt = ofile.kind, as dpkt.py:179 does. History: 74707ebc8 (2023-04-27) removed ext.record_header() from this engine, and that call had set _offmt as a side effect of dumping the global header. DPKT sets _offmt itself, but Scapy never did. This PR follows DPKT and does not restore record_header, whose future is chore(foundation): decide the fate of the unused public Extractor.record_header #1104.

Probe (base b10e7951b → this branch): message 'format' → 'output'. After make_name(..., 'bogus'), 'bogus' in __output__ was True with 8→9 keys and is now False with 8→8. Scapy .format raised AttributeError: ... '_offmt' and now returns json.

Tests: with the fix reverted, tests/foundation/test_extraction_output_offmt_unit.py reports 3 failed. With the fix, it reports 3 passed. The other modules: test_extraction.py 22 passed, engines/test_scapy_engine.py 2 passed, engines/test_runtime_engines.py 5 passed, and tests/project 379 passed, 1 skipped.

[JarryShaw]

Cross-review verdict on 2c285dd11: GOOD TO GO (ran on Sonnet; author Opus)

• _offmt fix: scapy now sets _offmt per frame, the same way dpkt.py:179 does. A real scapy run gives .format of json, txt and plist, including files=True.
• History: confirmed that 74707ebc8 dropped record_header(), which had been setting _offmt as a side effect.
• make_name: it still raises the same FormatError for an unknown format, and the registry keys are now unchanged.
• Other subscript: the one at Extractor.__init__ (~1181) can't be reached with an unknown format.
• Tests: with the source reverted, the 3 new tests fail. test_extraction (22) and test_scapy_engine (2) pass.

Known limits, not regressions:

• A capture with no frames still leaves scapy's _offmt unset, as it does for DPKT.
• Scapy with format='pcap' raises TypeError in PCAPIO.__init__. That path is untouched by this PR.

[github-actions]

Coverage: 88.74% (unit tier, Python 3.14, 2c285dd11, Unit Tests run success)

Package	Statements	Missed	Branches	Partial	Cover
pcapkit (top level)	104	4	20	4	93.55%
pcapkit/const	18757	1035	2342	846	90.23%
pcapkit/corekit	1874	91	578	22	94.33%
pcapkit/dumpkit	136	0	40	0	100.00%
pcapkit/foundation	2425	145	842	34	92.56%
pcapkit/interface	112	7	40	5	92.11%
pcapkit/protocols	15653	187	3942	162	98.19%
pcapkit/toolkit	487	71	144	3	84.15%
pcapkit/utilities	429	4	122	4	98.55%
pcapkit/vendor	4409	2359	1006	158	42.84%

Per-file detail: the coverage-html artifact of this run.