ESD-1650: Polish WASM output composition and HTTP transport fidelity

[Phil-Browne]

Three fidelity gaps in the WASM build. The command tree stays alive across invocations in a browser session, so repeated --help calls kept re-coloring and re-suffixing the same help text. Structured output (JSON/CSV/XML/table) was overwritten on every print call, so a command emitting more than one document only kept the last. And the WASM HTTP transport dropped every header value but the first and sent bodies as Go strings, which would mangle a binary body.

• Cache each command's pristine help text so repeated --help always renders from a clean base.
• Accumulate structured output buffers across calls within one command, clearing only between invocations.
• Join multi-value headers instead of dropping all but the first, and send request bodies as raw bytes via a Uint8Array.
• Roll back a structured buffer to its pre-call length if an encode fails partway through, so a failed call can't leak partial output into a later successful one.

Tests added for the help-text regression, buffer accumulation (including a first-ever XML output test), and the transport header/body fixes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.29%. Comparing base (dee5b8d) to head (4cb5846).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #534   +/-   ##
=======================================
  Coverage   79.29%   79.29%           
=======================================
  Files         193      193           
  Lines       18683    18685    +2     
=======================================
+ Hits        14814    14816    +2     
  Misses       2820     2820           
  Partials     1049     1049           

Files with missing lines	Coverage Δ
internal/base/output/common.go	77.70% <100.00%> (+0.14%)	⬆️

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[Copilot]

Pull request overview

This PR addresses statefulness and fidelity issues specific to the js/wasm build, where the Cobra command tree and WASM output/transport layers persist across browser-session invocations. It prevents repeated help rendering from re-mutating the same cmd.Long, ensures structured output buffers (JSON/CSV/XML/table) accumulate within a single invocation but reset between invocations, and improves HTTP request transport fidelity for multi-value headers and binary request bodies.

Changes:

• Cache each command’s pristine Long help text in WASM so repeated --help renders from an unmodified baseline.
• Change WASM structured output writers to append per PrintOutput call (with rollback-on-encode-failure) and reset those buffers between WASM invocations via output.ResetState().
• Fix WASM fetch option composition to (1) join multi-value request headers and (2) send request bodies as raw bytes via Uint8Array instead of UTF-8 strings; add tests for these behaviors.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/wasm/wasmhttp/transport.go	Joins multi-value request headers and sends request bodies as Uint8Array to avoid binary mangling.
internal/wasm/wasmhttp/transport_test.go	Adds tests for multi-value header joining and binary body round-tripping through fetch options.
internal/base/output/table_wasm.go	Appends table output across calls (per invocation) and prints only the newly-rendered segment.
internal/base/output/table_wasm_test.go	Adds a regression test ensuring multiple table renders are accumulated.
internal/base/output/output_wasm.go	Appends JSON/CSV/XML output across calls with rollback-on-error; wires a WASM reset hook to clear buffers between invocations.
internal/base/output/output_wasm_test.go	Adds accumulation tests for JSON/CSV/XML plus a first XML WASM capture test and ResetState buffer-clear test.
internal/base/output/common.go	Extends ResetState() to also clear WASM structured buffers via an overridable hook.
cmd/megaport/megaport_wasm.go	Caches original per-command Long help text to prevent repeated --help from re-coloring/re-suffixing already-mutated content.
cmd/megaport/help_wasm_test.go	New WASM tests asserting repeated --help invocations produce byte-identical output for root and a subcommand.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

[penzeliz-megaport]

Reviewed for correctness; no findings. LGTM.

[Phil-Browne]

Merge conflicts resolved @penzeliz-megaport