feat: support implicit template placeholders

[RAprogramm]

Summary

• allow {}/{:?} placeholders by introducing TemplateIdentifier::Implicit with sequential numbering and parser diagnostics for whitespace-only bodies
• propagate implicit identifiers through derive metadata and Display generation to resolve tuple fields in placeholder order
• bump masterror workspace crates to 0.6.0/0.2.0 and document the new behaviour with parser/unit regressions

Testing

• cargo +nightly fmt --
• cargo +1.90.0 clippy -- -D warnings
• cargo +1.90.0 build --all-targets
• cargo +1.90.0 test --all
• cargo +1.90.0 doc --no-deps
• cargo +1.90.0 deny check
• cargo +1.90.0 audit

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https://chatgpt.com/codex/tasks/task_e_68cd5ddef848832b98f1680112db4a05