feat(Logic.Equiv.BijectiveBase2): add bijective base-2 numeration

[AlexeyMilovanov]

This PR introduces a formalization of the bijective base-2 numeration system.

Unlike standard binary representation, bijective base-2 avoids the "leading zeros" problem, providing a strict mathematical bijection between natural numbers (ℕ) and lists of booleans (List Bool).

Main additions:

• Equiv.BijectiveBase2.toBits: Encodes ℕ to List Bool.
• Equiv.BijectiveBase2.ofBits: Decodes List Bool to ℕ.
• equivBijectiveBase2: The formal ℕ ≃ List Bool equivalence.

(Note: This replaces my previously closed PR to avoid the terminology clash between "Dyadic" and dyadic rationals. The namespace and definitions have been updated accordingly).

(Note: Used AI to assist with standardizing proof structures).

[github-actions]

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[github-actions]

PR summary 7dfb413d60

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Logic.Equiv.ListNatBijective (new file)	290

---

Declarations diff

+ listNatBijectiveEquiv
+ ofBits
+ ofBits_nil
+ ofBits_toBits
+ toBits
+ toBits_ofBits
+ toBits_zero

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for scripts/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).