Fix factual and spec errors in docs content

[externl]

Fixes ~35 factual errors across 25 content pages, found during a full editorial review. Every claim was verified against slicec 0.4.0 (the version icerpc-csharp 0.6 pins), the icerpc-csharp generators, or recomputed by hand.

Slice encoding

• user-defined-types.md — the worked example encoded tag 2 as 0x10; a varint32 of 2 on 1 byte is 0x08
• icerpc.md — the stream argument / stream return value pairing was swapped between outgoing request and response
• primitive-types.md — varuint62 vs QUIC: byte order is not the only difference; QUIC stores the 2-bit length in the most significant bits of the first byte, Slice in the least significant bits

Slice grammar reference (brought back in sync with slicec 0.4.0)

• Enum production gains "compact"? — placed before "unchecked"?, matching the parser
• Enumerator production gains the variant field list ("(" UndelimitedList<Field> ")")?
• FileAttribute/LocalAttribute now use the bracket tokens ([[ ]] / [ ]) instead of nonexistent/wrong brace tokens
• removed the stale FileCompilationMode production and its SliceFilePrelude alternatives — the mode statement no longer exists in slicec 0.4.0 (it referenced a mode_keyword token that was never defined anyway)
• removed CompactId (referenced by nothing) and ThrowsBlock/throws_keyword (slicec has no @throws)
• renamed the preprocessor lexical token to undefine_keyword to match the syntactic grammar
• prose: fields can also appear in enumerators, doc comments on parameters are forbidden, tag numbers are non-negative, and 0x_ab_cd_ef is 0xabcdef

Language guide & basics

• DefaultServicePath sample → "/Example.Widget" (:: → ., per the generator)
• block comments do not nest
• only basic enums (with an underlying type) can be dictionary keys
• reworked the circular-import example in slice-files.md — it used invalid syntax (Egg lay()) and interfaces as return types; the two files now exchange structs
• "two built-in generic types" → three (adds Result)
• doc-comment examples: removed the nonexistent @param color and stopped returning interface Widget directly
• cs::encodeReturn → cs::encodedReturn (per the generator source)
• the sequence fast path covers fixed-size numeric (not just integral) types
• the Slic Version frame carries varuint62 (not varint62) values

Getting started (0.6 template drift)

• contract paths → slice/VisitorCenter/Greeter.slice and proto/visitor_center/greeter.proto (matching the 0.6 templates and the pages' own screenshots)
• --transport is only defined by the non-DI templates
• Slice compilation produces generated/Greeter.cs and generated/Greeter.IceRpc.cs
• the Slice server tutorial now covers Program.Authentication.cs like its three sibling tutorials

Misc

• un-merged two accidentally joined bullets on the DI page
• dropped the outdated "a priority queue … is not a standard C# container" claim (PriorityQueue<TElement, TPriority> exists since .NET 6)
• proxies are "concrete types" (record structs), modules also scope interfaces, "proxy" → "client" in the Protobuf tutorial, and a comment for the CancelKeyPressed helper

Deliberate skip: the source_block; notation nit — the existing comment in the grammar already explains it.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates the documentation set to correct a broad set of factual/spec mismatches (Slice grammar reference, encoding examples, and getting-started/tutorial content) so the published docs align with actual slicec parsing behavior, generator outputs, and on-the-wire encoding.

Changes:

• Sync Slice grammar reference pages with slicec behavior (enum modifiers/grammar productions, attribute tokens, token naming).
• Fix Slice encoding documentation inaccuracies (tag example byte, varuint62 vs QUIC details, request/response stream continuation description).
• Update getting-started tutorials and other guides for template drift, naming, and corrected examples.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
content/slice/language-reference/slice-grammar.md	Align grammar + prose with slicec (enum/attributes/tokens) and fix several factual notes/examples.
content/slice/language-reference/preprocessor-directives.md	Rename the #undef token name to match the syntactic grammar.
content/slice/language-reference/doc-comments.md	Remove unsupported @throws grammar elements.
content/slice/language-guide/sequence-types.md	Correct C# fast-path wording to “fixed-size numeric” types.
content/slice/language-guide/operation.md	Fix cs::encodedReturn attribute name and grammar in prose.
content/slice/language-guide/module.md	Clarify that modules scope interfaces as well as types.
content/slice/language-guide/interface.md	Correct wording around proxies and fix DefaultServicePath example.
content/slice/language-guide/dictionary-types.md	Clarify dictionary key constraints (basic enums).
content/slice/language-guide/comments.md	Correct block comment nesting claim and doc-comment example signatures.
content/slice/language-guide/attributes.md	Fix cs::encodedReturn attribute name in the attribute table.
content/slice/index.md	Update built-in generic types count and add Result link.
content/slice/encoding/user-defined-types.md	Fix tagged-field worked example (tag byte).
content/slice/encoding/primitive-types.md	Correct varuint62 vs QUIC comparison details.
content/slice/encoding/icerpc.md	Fix request/response stream continuation pairing description.
content/slice/basics/slice-files.md	Replace invalid circular-reference example with valid cross-file struct/interface usage.
content/slice/basics/examples.md	Remove nonexistent doc-comment @param color in example.
content/icerpc/slic-transport/protocol-frames.md	Fix Version frame value type name (varuint62).
content/icerpc/dependency-injection/di-and-icerpc-for-csharp.md	Split/clarify accidentally merged DI bullet list.
content/icerpc-for-ice-users/rpc-core/object-adapter.md	Clarify what CancelKeyPressed represents in the snippet.
content/icerpc-for-ice-users/ice-definitions/sequence-types.md	Remove outdated claim about priority queue availability in .NET.
content/getting-started/installation/template.md	Clarify --transport support scope (non-DI templates).
content/getting-started/icerpc-slice-tutorial/server-tutorial.md	Update template paths/output files and document Program.Authentication.cs.
content/getting-started/icerpc-slice-tutorial/client-tutorial.md	Update template paths and generated output files.
content/getting-started/icerpc-protobuf-tutorial/server-tutorial.md	Update proto contract path to match templates.
content/getting-started/icerpc-protobuf-tutorial/client-tutorial.md	Update proto contract path and “proxy” → “client” wording.

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[externl]

This matches slicec's actual parser: the Tag rule in grammar.lalrpop is tag_keyword "(" SignedInteger ")" (same on 0.6-era v0.3.3), and parse_tag_value rejects negatives afterwards as a semantic error. The grammar production is faithful to the parser; "non-negative" (like the 2,147,483,647 max on the next line) is a semantic constraint the grammar deliberately doesn't encode. Keeping SignedInteger.

[externl]

Correction on the version cited here: icerpc-csharp 0.6 pins slicec 0.4.0, not 0.3.x — the Tag rule is identical there (tag_keyword "(" SignedInteger ")" with parse_tag_value rejecting negatives), so the conclusion stands.

[externl]

Same as the section grammar: slicec's parser really does accept a SignedInteger here and rejects negative values during validation, so the production matches the parser. Keeping SignedInteger.

[externl]

Same correction as above: verified against slicec 0.4.0 (what 0.6 pins) — identical rule, conclusion stands.

[bernardnormier]

Looks good.

[bernardnormier]

This is a good fix. The previous example relied on proxy custom types (with the custom not shown), which was confusing.