docs(adr): record that the Gradle exclude residue was measured, not assumed

[rodrigorjsf]

Closes #91 once merged, by taking its option 1 — accept the residue — with the measurement its
acceptance criteria required.

What #91 left open

The Gradle exclude recognizer shipped in #68 keeps two residual holes: an unclosed exclude( with
an orphan ) and no brace between them, and a Groovy exclude line whose trailing comma is followed
by a declaration. Both blank a real langchain4j-…shell… declaration — a false negative, the failure
#45 exists to prevent.

#91's acceptance criteria let the issue close as accepted only with ADR 0007 amended to say the
residue was measured and kept. Nothing had measured it: #88's survey read 262 build files for
refusal spellings, not for these two shapes.

What was measured

Both shapes were first re-verified against shell_artifact_declarations on current main
(d5e9682), each with a control, so the mechanism is isolated rather than assumed:

input	result
shape A	{}
shape A, exclude( line deleted	ShellDeclaration(line=2, langchain4j-experimental-skills-shell)
shape B	{}
shape B, trailing comma dropped	ShellDeclaration(line=3, langchain4j-experimental-skills-shell)

Then the shipped _GRADLE_EXCLUDE_CALL was run over #88's downloaded population — all 262 files —
looking for the hazard both shapes share, shape-agnostically: a match that spans lines and swallows a
line opening a dependency declaration (implementation, api, testImplementation, …).

files scanned: 262
multi-line exclude matches: 4
matches swallowing a declaration line: 0
control A: detector fires = True
control B: detector fires = True

The four multi-line matches are the four wrapped exclude( calls #88 already classified as file
filters. The two controls prove the zero is not vacuous.

What this PR changes

One paragraph in docs/adr/0007-l4j-shell-survives-the-graduation-rename.md, plus one Applied
Learning bullet in CLAUDE.md recording that #88's population is still on disk — the fact that made
this measurement free. No code, no test, no
snapshot — tests/behavior/snapshots/langchain4j_gradle_skill.json is untouched, as #91's third
acceptance criterion requires.

The amendment says rarity, not impossibility: the population is filtered to build files naming
both langchain4j and exclude, so a zero there bounds how often the shapes occur near the code
this Rule reads — it does not prove they cannot exist.

Deliberately not done

Options 2–4 of #91. Two of them trade one residue for another (an arbitrary line cap; a vocabulary of
Gradle configuration names to keep true), and the third reverses the no-brace-parsing decision
signals.py is built on. Zero observed instances does not buy any of that.

Validation

• make lint — passed
• make format-check — 204 files already formatted
• make test-unit — 2639 passed, 12 skipped, 4 xfailed
• make update-snapshots — tree clean afterwards (git status empty)
• CI green on 8734c2c: test-unit, lint, DCO Check, changes all pass
• prose-only diff; no snapshot regeneration needed