refactor(mining): unify block template naming

[illuzen]

Problem

The candidate block being mined is referred to by four different names across the mining code: MiningBuild/"build" in code, "block template" and "candidate" in comments and logs, and "proposal" via the inner Substrate type. On top of that, the bare Version type doesn't say what it is a version of (it tracks template generations, not software versions).

Change

Standardize on template as the canonical noun, matching standard PoW terminology:

• MiningBuild → BlockTemplate
• Version → TemplateVersion, VersionSignal → TemplateVersionSignal
• MiningHandle::version() → template_version()
• wait_for_version_change() → wait_for_template_change()
• on_build() → on_new_template(), create_proposal() → create_block_template()
• pending_build → pending_rebuild (it holds a rebuild request hash, not a build)
• comments/logs saying "build"/"candidate" now say "template"

"Job" is intentionally unchanged in miner_server.rs — it is a distinct concept (the wire-protocol message broadcast to external miners).

Pure rename on top of #700; no behavior changes.

Validation

• SKIP_WASM_BUILD=1 cargo test -p sc-consensus-qpow: 13 passed
• SKIP_WASM_BUILD=1 cargo test -p quantus-node --bin quantus-node: 62 passed
• ./clippy.sh clean
• After rebasing onto the perf(mining): eliminate polling delays when block templates change #700 squash-merge, the resulting tree is byte-identical to the tested one (git diff empty)

[n13]

Reviewer model: GPT-6 Astra

APPROVE — no blocking findings.

Reviewed the complete three-file diff at 04f2daa11c58cebc010bac6227e4e365cc33e219 against 662ef6d1dea8f3572776b8db9da1f57283744fd2. The template/type/method renames are consistent across construction, cloning, submission, and both mining paths. Template generation tracking, cancellation, lock boundaries, seal verification, and the external-miner wire protocol retain their behavior.

Validation:

• git diff --check and locked Cargo metadata — passed.
• taplo format --check --config taplo.toml and scripts/fmt.sh --all -- --check — passed.
• SKIP_WASM_BUILD=1 cargo test --locked -p sc-consensus-qpow — 13 passed, including retained notifications, multiple waiters, and cancellation.
• SKIP_WASM_BUILD=1 cargo test --locked -p quantus-node --bin quantus-node — 62 passed, including cancellation of result reception.
• SKIP_WASM_BUILD=1 cargo clippy --locked -p sc-consensus-qpow -p quantus-node --all-targets -- -D warnings — passed.
• SKIP_WASM_BUILD=1 RUSTDOCFLAGS='-D warnings' cargo doc --locked --no-deps -p sc-consensus-qpow -p quantus-node — passed.

The tests and formatting checks ran before the rebase at a19db21b; I verified that its Git tree is identical to the current head (9f7bdcc4b5b3259bac19ce2f1076f952940f4af9). Clippy and rustdoc ran at the current head. Full Linux/macOS CI and CI analysis were still running at review time.

[n13]

Not reviewing again — no new commit or comment since the last review.