Fix #639: don't flag self-aliases used in nested formations

[bibonix]

@yegor256 this PR fixes #639. Here's what changed and why:

The bug

The example from the issue:

[] > jeff
  $ > self
  [] > say-hello
    stdout self > @

raised The object "self" is redundant and may be inlined. You confirmed it was a false positive.

Root cause

redundant-object.xsl flags any named, non-φ object whose @base reference appears at most once in the program. The parser emits the only reference to self from inside say-hello as <o base="ξ.ρ.self"/>, so the count is 1 and the lint fires.

The match itself is fine — the suggested remediation (inlining) is what would be unsafe. self's body is $ (@base="ξ"), and inlining $ into a nested formation changes its meaning, since ξ inside say-hello refers to say-hello, not to jeff. The fix has to suppress the warning specifically for that shape.

Fix

src/main/resources/org/eolang/lints/misc/redundant-object.xsl: add a second regex that captures only references reached through a parent hop (^ξ\.ρ(?:\.ρ)*\.<name>(?:\.[\w-]+)*$), and skip the warning when the candidate's @base="ξ" and at least one of its usages matches that nested-reference regex. Same-level usages of a $-alias remain flagged because they can be safely inlined.

Test

Added pack redundant-object/allows-self-reused-in-nested-formation.yaml with the exact snippet from the issue, asserting zero defects. It fails on the pre-fix XSL and passes after.

CI

Lint-only checks (qulice, pdd, ort, xcop, yamllint, markdown-lint, vale, actionlint, shellcheck, reuse, copyrights, bashate, typos, labeler) all pass.

The mvn matrix, deep, and reserved jobs are red, but they are red on master too — every push since 2026-04-25 has failed them (run 24960783274 on master, your most recent push, fails the same way). The failures are timeouts in MonoLintsTest.lintsProgramCorrectly and PkByXslTest.doesNotDuplicateDefectsWhenMultipleDefectsOnTheSameLine after 45s, which I reproduced locally on a clean checkout of master before applying my fix. Happy to open a separate ticket for the timeouts if useful.

Test plan

• New pack allows-self-reused-in-nested-formation.yaml reproduces the issue and passes after the fix.
• All other redundant-object packs still pass (8 allow + 7 catch).
• Full LtByXslTest passes locally (357 tests, 1 skipped).

Ready for merge.